hydrogen
hydrogen: n. Chem. a colourless gaseous element, without taste or odour, the lightest of the elements and occurring in water and all organic compounds. Symb.: H. hydrogen bomb an immensely powerful bomb utilizing the explosive fusion of hydrogen nuclei: also called H-BOMB. hydrogen bond a weak electrostatic interaction between an electronegative atom and a hydrogen atom bonded to a different electronegative atom. hydrogen peroxide a colourless viscous unstable liquid with strong oxidizing properties. Chem. formula: H[2]O[2]. hydrogen sulphide a colourless poisonous gas with a disagreeable smell, formed by rotting animal matter. Chem. formula: H[2]S. hydrogenous adj. [F hydrogne (as HYDRO-, -GEN)]

hectare
hectare: n. a metric unit of square measure, equal to 100 ares (2.471 acres or 10,000 square metres). hectarage n. [F (as HECTO-, ARE(2))]

histrionic
histrionic: adj. & n. --adj.
1 of or concerning actors or acting.
2 (of behaviour) theatrical, dramatic. --n.
1 (in pl.) a insincere and dramatic behaviour designed to impress. b theatricals; theatrical art.
2 archaic an actor. histrionically adv. [LL histrionicus f. L histrio -onis actor]

headache
headache: n.
1 a continuous pain in the head.
2 colloq. a a worrying problem. b a troublesome person. headachy adj.

hear
hear: v. (past and past part. heard.
1 tr. (also absol.) perceive (sound etc.) with the ear.
2 tr. listen to (heard them on the radio).
3 tr. listen judicially to and judge (a case, plaintiff, etc.).
4 intr. (foll. by about, of, or that + clause) be told or informed.
5 intr. (foll. by from) be contacted by, esp. by letter or telephone.
6 tr. be ready to obey (an order).
7 tr. grant (a prayer). have heard of be aware of; know of the existence of. hear! hear! int. expressing agreement (esp. with something said in a speech). hear a person out listen to all that a person says. hear say (or tell) (usu. foll. by of, or that + clause) be informed. will not hear of will not allow or agree to. hearable adj. hearer n. [OE hieran f. Gmc]

hunk
hunk: n.
1 a a large piece cut off (a hunk of bread). b a thick or clumsy piece.
2 colloq. a a very large person. b esp. US a sexually attractive man. hunky adj. (hunkier, hunkiest). [19th c.: prob. f. Flem. hunke]

haemorrhage
haemorrhage: n. & v. (US hemorrhage) --n.
1 an escape of blood from a ruptured blood-vessel, esp. when profuse.
2 an extensive damaging loss suffered by a State. organization, etc., esp. of people or assets. --v.intr. undergo a haemorrhage. haemorrhagic adj. [earlier haemorrhagy f. F hmorr(h)agie f. L haemorrhagia f. Gk haimorrhagia f. haima blood + stem of rhegnumi burst]

harness
harness: n. & v. --n.
1 the equipment of straps and fittings by which a horse is fastened to a cart etc. and controlled.
2 a similar arrangement for fastening a thing to a person's body, for restraining a young child, etc. --v.tr.
1 a put a harness on (esp. a horse). b (foll. by to) attach by a harness.
2 make use of (natural resources) esp. to produce energy. in harness in the routine of daily work. harnesser n. [ME f. OF harneis military equipment f. ON hernest (unrecorded) f. herr army + nest provisions]

halloo
halloo: int., n., & v. --int.
1 inciting dogs to the chase.
2 calling attention.
3 expressing surprise. --n. the cry 'halloo'. --v. (halloos, hallooed.
1 intr. cry 'halloo', esp. to dogs.
2 intr. shout to attract attention.
3 tr. urge on (dogs etc.) with shouts. [perh. f. hallow pursue with shouts f. OF halloer (imit.)]

hallelujah
hallelujah: var. of ALLELUIA.

herald
herald: n. & v. --n.
1 an official messenger bringing news.
2 a forerunner (spring is the herald of summer).
3 a hist. an officer responsible for State ceremonial and etiquette. b Brit. an official of the Heralds' College. --v.tr. proclaim the approach of; usher in (the storm heralded trouble). Heralds' College Brit. colloq. = College of Arms. [ME f. OF herau(l)t, herauder f. Gmc]

haematocrit
haematocrit: n. (US hematocrit) Physiol.
1 the ratio of the volume of red blood cells to the total volume of blood.
2 an instrument for measuring this. [HAEMATO- + Gk krites judge]

histogram
histogram: n. Statistics a chart consisting of rectangles (usu. drawn vertically from a base line) whose areas and positions are proportional to the value or range of a number of variables. [Gk histos mast + -GRAM]

haemophilia
haemophilia: n. (US hemophilia) Med. a usu. hereditary disorder with a tendency to bleed severely from even a slight injury, through the failure of the blood to clot normally. haemophilic adj. [mod.L (as HAEMO-, -PHILIA)]

habitual
habitual: adj.
1 done constantly or as a habit.
2 regular, usual.
3 given to a (specified) habit (a habitual smoker). habitually adv. habitualness n. [med.L habitualis (as HABIT)]

harmony
harmony: n. (pl. -ies.
1 a a combination of simultaneously sounded musical notes to produce chords and chord progressions, esp. as having a pleasing effect. b the study of this.
2 a an apt or aesthetic arrangement of parts. b the pleasing effect of this.
3 agreement, concord.
4 a collation of parallel narratives, esp. of the Gospels. in harmon.
1 (of singing etc.) producing chords; not discordant.
2 (often foll. by with) in agreement. harmony of the spheres see SPHERE . [ME f. OF harmonie f. L harmonia f. Gk harmonia joining, concord, f. harmos joint]

honeymoon
honeymoon: n. & v. --n.
1 a holiday spent together by a newly married couple.
2 an initial period of enthusiasm or goodwill. --v.intr. (usu. foll. by in, at) spend a honeymoon. honeymooner n. [HONEY + MOON, orig. with ref. to waning affection, not to a period of a month]

hibiscus
hibiscus: n. any tree or shrub of the genus Hibiscus, cultivated for its large bright-coloured flowers. Also called rose-mallow. [L f. Gk hibiskos marsh mallow]

hangman
hangman: n. (pl. -men.
1 an executioner who hangs condemned persons.
2 a word-game for two players, in which the tally of failed guesses is kept by drawing a representation of a gallows.

hospital
hospital: n.
1 an institution providing medical and surgical treatment and nursing care for ill or injured people.
2 hist. a a hospice. b an establishment of the Knights Hospitallers.
3 Law a charitable institution (also in proper names, e.g. Christ's Hospital). hospital corners a way of tucking in sheets, used by nurses. hospital fever a kind of typhus formerly prevalent in crowded hospitals. hospital ship a ship to receive sick and wounded seamen, or to take sick and wounded soldiers home. hospital train a train taking wounded soldiers from a battlefield. [ME f. OF f. med.L hospitale neut. of L hospitalis (adj.) (as HOST(2))]

hallucination
hallucination: n. the apparent or alleged perception of an object not actually present. hallucinatory adj. [L hallucinatio (as HALLUCINATE)]

herpes
herpes: n. a virus disease with outbreaks of blisters on the skin etc. herpes simplex a viral infection which may produce blisters or conjunctivitis. herpes zoster = SHINGLES. herpetic adj. [ME f. L f. Gk herpes -etos shingles f. herpo creep: zoster f. Gk zoster belt, girdle]

handbag
handbag: n. & v. --n. a small bag for a purse etc., carried esp. by a woman. --v.tr. (of a woman politician) treat (a person, idea, etc.) ruthlessly or insensitively.

halfpenny
halfpenny: n. (also ha'penny) (pl. -pennies or -pence) (in the UK) a former bronze coin worth half a penny. Withdrawn in 1984. (cf. FARTHING).

halcyon
halcyon: adj. & n. --adj.
1 calm, peaceful (halcyon days).
2 (of a period) happy, prosperous. --n.
1 any kingfisher of the genus Halcyon, native to Europe, Africa, and Australasia, with brightly-coloured plumage.
2 Mythol. a bird thought in antiquity to breed in a nest floating at sea at the winter solstice, charming the wind and waves into calm. [ME f. L (h)alcyon f. Gk (h)alkuon kingfisher]

hermaphrodite
hermaphrodite: n. & adj. --n.
1 a Zool. an animal having both male and female sexual organs. b Bot. a plant having stamens and pistils in the same flower.
2 a human being in which both male and female sex organs are present, or in which the sex organs contain both ovarian and testicular tissue.
3 a person or thing combining opposite qualities or characteristics. --adj.
1 combining both sexes.
2 combining opposite qualities or characteristics. hermaphrodite brig hist. a two-masted sailing ship rigged on the foremast as a brig and on the mainmast as a schooner. hermaphroditic adj. hermaphroditical adj. hermaphroditism n. [L hermaphroditus f. Gk hermaphroditos, orig. the name of a son of Hermes and Aphrodite in Greek mythology, who became joined in one body with the nymph Salmacis]

horoscope
horoscope: n. Astrol.
1 a forecast of a person's future based on a diagram showing the relative positions of the stars and planets at that person's birth.
2 such a diagram (cast a horoscope).
3 observation of the sky and planets at a particular moment, esp. at a person's birth. horoscopic adj. horoscopical adj. horoscopy n. [F f. L horoscopus f. Gk horoskopos f. hora time + skopos observer]

haunterhafiz
hafiz: n. a Muslim who knows the Koran by heart. [Pers. f. Arab. hafiz guardian]

holocaust
holocaust: n.
1 a case of large-scale destruction, esp. by fire or nuclear war.
2 (the Holocaust) the mass murder of the Jews by the Nazis 1939-45.
3 a sacrifice wholly consumed by fire. [ME f. OF holocauste f. LL holocaustum f. Gk holokauston (as HOLO-, kaustos burnt f. kaio burn)]

history
history: n. (pl. -ies.
1 a continuous, usu. chronological, record of important or public events.
2 a the study of past events, esp. human affairs. b the total accumulation of past events, esp. relating to human affairs or to the accumulation of developments connected with a particular nation, person, thing, etc. (our island history; the history of astronomy).
3 an eventful past (this house has a history).
4 a a systematic or critical account of or research into a past event or events etc. b a similar record or account of natural phenomena.
5 a historical play. make histor.
1 influence the course of history.
2 do something memorable. [ME f. L historia f. Gk historia finding out, narrative, history f. histor learned, wise man, rel. to WIT(2)]

heald
heald: n. = HEDDLE. [app. f. OE hefel, hefeld, f. Gmc]

hertz
hertz: n. (pl. same) the SI unit of frequency, equal to one cycle per second. Abbr.: Hz. [H. R. Hertz, Ger. physicist d. 1894]

human
human: adj. & n. --adj.
1 of or belonging to the genus Homo.
2 consisting of human beings (the human race).
3 of or characteristic of mankind as opposed to God or animals or machines, esp. susceptible to the weaknesses of mankind (is only human).
4 showing (esp. the better) qualities of man (proved to be very human). --n. a human being. human being any man or woman or child of the species Homo sapiens. human chain a line of people formed for passing things along, e.g. buckets of water to the site of a fire. human engineerin.
1 the management of industrial labour, esp. as regards man-machine relationships.
2 the study of this. human equation a bias or prejudice. human interest (in a newspaper story etc.) reference to personal experience and emotions etc. human nature the general characteristics and feelings of mankind. human relations relations with or between people or individuals. human rights rights held to be justifiably belonging to any person. humanness n. [ME humain(e) f. OF f. L humanus f. homo human being]

hamster
hamster: n. any of various rodents of the subfamily Cricetinae, esp. Cricetus cricetus, having a short tail and large cheek pouches for storing food, kept as a pet or laboratory animal. [G f. OHG hamustro corn-weevil]

heaven
heaven: n.
1 a place regarded in some religions as the abode of God and the angels, and of the good after death, often characterized as above the sky.
2 a place or state of supreme bliss.
3 colloq. something delightful.
4 (usu. Heaven) God, Providence (often, in sing. or pl. as an exclam. or mild oath: by Heaven).
5 (the heavens) esp. poet. the sky as the abode of the sun, moon, and stars and regarded from earth. heaven-sent providential; wonderfully opportune. in seventh heaven in a state of ecstasy. move heaven and earth (foll. by to + infin.) make extraordinary efforts. heavenward adj. & adv. heavenwards adv. [OE heofon]

hepatitis
hepatitis: n. inflammation of the liver. [mod.L: see HEPATIC]

hardware
hardware: n.
1 tools and household articles of metal etc.
2 heavy machinery or armaments.
3 the mechanical and electronic components of a computer etc. (cf. SOFTWARE).

honestly
honestly: adv.
1 in an honest way.
2 really (I don't honestly know; honestly, the cheek of it!).

hagiography
hagiography: n. the writing of the lives of saints. hagiographic adj. hagiographical adj.

head
head: n., adj., & v. --n.
1 the upper part of the human body, or the foremost or upper part of an animal's body, containing the brain, mouth, and sense-organs.
2 a the head regarded as the seat of intellect or repository of comprehended information. b intelligence; imagination (use your head). c mental aptitude or tolerance (usu. foll. by for: a good head for business; no head for heights).
3 colloq. a headache, esp. resulting from a blow or from intoxication.
4 a thing like a head in form or position, esp.: a the operative part of a tool. b the flattened top of a nail. c the ornamented top of a pillar. d a mass of leaves or flowers at the top of a stem. e the flat end of a drum. f the foam on top of a glass of beer etc. g the upper horizontal part of a window frame, door frame, etc.
5 life when regarded as vulnerable (it cost him his head).
6 a a person in charge; a director or leader (esp. the principal teacher at a school or college). b a position of leadership or command.
7 the front or forward part of something, e.g. a queue.
8 the upper end of something, e.g. a table or bed.
9 the top or highest part of something, e.g. a page, stairs, etc. 10 a person or individual regarded as a numerical unit (10 per head). 11 (pl. same) a an individual animal as a unit. b (as pl.) a number of cattle or game as specified (20 head). 12 a the side of a coin bearing the image of a head. b (usu. in pl.) this side as a choice when tossing a coin. 13 a the source of a river or stream etc. b the end of a lake at which a river enters it. 14 the height or length of a head as a measure. 15 the component of a machine that is in contact with or very close to what is being processed or worked on, esp.: a the component on a tape recorder that touches the moving tape in play and converts the signals. b the part of a record-player that holds the playing cartridge and stylus. c = PRINTHEAD. 16 a a confined body of water or steam in an engine etc. b the pressure exerted by this. 17 a promontory (esp. in place-names) (Beachy Head). 18 Naut. a the bows of a ship. b (often in pl.) a ship's latrine. 19 a main topic or category for consideration or discussion. 20 Journalism = HEADLINE n. 21 a culmination, climax, or crisis. 22 the fully developed top of a boil etc. 23 sl. a habitual taker of drugs; a drug addict. --attrib.adj. chief or principal (head gardener; head office). --v.
1 tr. be at the head or front of.
2 tr. be in charge of (headed a small team).
3 tr. a provide with a head or heading. b (of an inscription, title, etc.) be at the top of, serve as a heading for.
4 a intr. face or move in a specified direction or towards a specified result (often foll. by for: is heading for trouble). b tr. direct in a specified direction.
5 tr. Football strike (the ball) with the head.
6 a tr. (often foll. by down) cut the head off (a plant etc.). b intr. (of a plant etc.) form a head. above (or over) one's head beyond one's ability to understand. come to a head reach a crisis. enter (or come into) one's head colloq. occur to one. from head to toe (or foot) all over a person's body. get one's head down sl.
1 go to bed.
2 concentrate on the task in hand. give a person his or her head allow a person to act freely. go out of one's head go mad. go to one's hea.
1 (of liquor) make one dizzy or slightly drunk.
2 (of success) make one conceited. head and shoulders colloq. by a considerable amount. head bac.
1 get ahead of so as to intercept and turn back.
2 return home etc. head-banger sl.
1 a young person shaking violently to the rhythm of pop music.
2 a crazy or eccentric person. head-butt n. a forceful thrust with the top of the head into the chin or body of another person. --v.tr. attack (another person) with a head-butt. head-dress an ornamental covering or band for the head. head firs.
1 with the head foremost.
2 precipitately. head in the sand refusal to acknowledge an obvious danger or difficulty. head of.
1 get ahead of so as to intercept and turn aside.
2 forestall. a head of hair the hair on a person's head, esp. as a distinctive feature. head-o.
1 with the front foremost (a head-on crash).
2 in direct confrontation. head over heel.
1 turning over completely in forward motion as in a somersault etc.
2 topsy-turvy.
3 utterly, completely (head over heels in love). head-shrinker sl. a psychiatrist. head start an advantage granted or gained at an early stage. heads will roll colloq. people will be disgraced or dismissed. head-up (of instrument readings in an aircraft, vehicle, etc.) shown so as to be visible without lowering the eyes. head-voice the high register of the voice in speaking or singing. head wind a wind blowing from directly in front. hold up one's head be confident or unashamed. in one's hea.
1 in one's thoughts or imagination.
2 by mental process without use of physical aids. keep one's head remain calm. keep one's head above water colloq.
1 keep out of debt.
2 avoid succumbing to difficulties. keep one's head down colloq. remain inconspicuous in difficult or dangerous times. lose one's head lose self-control; panic. make head or tail of (usu. with neg. or interrog.) understand at all. off one's head sl. crazy. off the top of one's head colloq. impromptu; without careful thought or investigation. on one's (or one's own) head as one's sole responsibility. out of one's hea.
1 sl. crazy.
2 from one's imagination or memory. over one's hea.
1 beyond one's ability to understand.
2 without one's knowledge or involvement, esp. when one has a right to this.
3 with disregard for one's own (stronger) claim (was promoted over their heads). put heads together consult together. put into a person's head suggest to a person. take (or get) it into one's head (foll. by that + clause or to + infin.) form a definite idea or plan. turn a person's head make a person conceited. with one's head in the clouds see CLOUD . headed adj. (also in comb.). headless adj. headward adj. & adv. [OE heafod f. Gmc]

hypnotic
hypnotic: adj. & n. --adj.
1 of or producing hypnotism.
2 (of a drug) soporific. --n.
1 a thing, esp. a drug, that produces sleep.
2 a person under or open to the influence of hypnotism. hypnotically adv. [F hypnotique f. LL hypnoticus f. Gk hupnotikos f. hupnoo put to sleep]

hidden
hidden: past part. of HIDE(1). hiddenness n.

hoarse
hoarse: adj.
1 (of the voice) rough and deep; husky; croaking.
2 having such a voice. hoarsely adv. hoarsen v.tr. & intr. hoarseness n. [ME f. ON hars (unrecorded) f. Gmc]

heed
heed: v. & n. --v.tr. attend to; take notice of. --n. careful attention. heedful adj. heedfully adv. heedfulness n. heedless adj. heedlessly adv. heedlessness n. [OE hedan f. WG]