occlusion
occlusion: n.
1 the act or process of occluding.
2 Meteorol. a phenomenon in which the cold front of a depression overtakes the warm front, causing upward displacement of warm air between them.
3 Dentistry the position of the teeth when the jaws are closed.
4 the blockage or closing of a hollow organ etc. (coronary occlusion).
5 Phonet. the momentary closure of the vocal passage. occlusive adj.

or
OR: abbr.
1 operational research.
2 US Oregon (in official postal use).
3 other ranks.

organic
organic: adj.
1 a Physiol. of or relating to a bodily organ or organs. b Med. (of a disease) affecting the structure of an organ.
2 (of a plant or animal) having organs or an organized physical structure.
3 Agriculture produced or involving production without the use of chemical fertilizers, pesticides, etc. (organic crop; organic farming).
4 Chem. (of a compound etc.) containing carbon (opp. INORGANIC).
5 a structural, inherent. b constitutional, fundamental.
6 organized, systematic, coordinated (an organic whole). organic chemistry the chemistry of carbon compounds. organic law a law stating the formal constitution of a country. organically adv. [F organique f. L organicus f. Gk organikos (as ORGAN)]

outside
outside: n., adj., adv., & prep. --n.
1 the external side or surface; the outer parts (painted blue on the outside).
2 the external appearance; the outward aspect of a building etc.
3 (of a path) the side away from the wall or next to the road.
4 (also attrib.) all that is without; the world as distinct from the thinking subject (learn about the outside world; viewed from the outside the problem is simple).
5 a position on the outer side (the gate opens from the outside).
6 colloq. the highest computation (it is a mile at the outside).
7 an outside player in football etc.
8 (in pl.) the outer sheets of a ream of paper. --adj.
1 of or on or nearer the outside; outer.
2 a not of or belonging to some circle or institution (outside help; outside work). b (of a broker) not a member of the Stock Exchange.
3 (of a chance etc.) remote; very unlikely.
4 (of an estimate etc.) the greatest or highest possible (the outside price).
5 (of a player in football etc.) positioned nearest to the edge of the field. --adv.
1 on or to the outside.
2 in or to the open air.
3 not within or enclosed or included.
4 sl. not in prison. --prep. (also disp. foll. by of.
1 not in; to or at the exterior of (meet me outside the post office).
2 external to, not included in, beyond the limits of (outside the law). at the outside (of an estimate etc.) at the most. get outside of sl. eat or drink. outside and in outside and inside. outside broadcast Brit. a broadcast made on location and not in a studio. outside edge (on an ice-skate) each of the edges facing outwards when both feet are together. outside in = inside out. outside interest a hobby; an interest not connected with one's work or normal way of life. outside seat a seat nearer the end of a row. outside track the outside lane of a sports track etc. which is longer because of the curve.

occupation
occupation: n.
1 what occupies one; a means of passing one's time.
2 a person's temporary or regular employment; a business, calling, or pursuit.
3 the act of occupying or state of being occupied.
4 a the act of taking or holding possession of (a country, district, etc.) by military force. b the state or time of this.
5 tenure, occupancy.
6 (attrib.) for the sole use of the occupiers of the land concerned (occupation road). [ME f. AF ocupacioun, OF occupation f. L occupatio -onis (as OCCUPY)]

offspring
offspring: n. (pl. same.
1 a person's child or children or descendant(s).
2 an animal's young or descendant(s).
3 a result. [OE ofspring f. OF from + springan SPRING v.]

official
official: adj. & n. --adj.
1 of or relating to an office (see OFFICE n. 5, 6) or its tenure or duties.
2 characteristic of officials and bureaucracy.
3 emanating from or attributable to a person in office; properly authorized.
4 holding office; employed in a public capacity.
5 Med. according to the pharmacopoeia, officinal. --n.
1 a person holding office or engaged in official duties.
2 (in full official principal) the presiding officer or judge of an archbishop's, bishop's, or esp. archdeacon's court. official birthday Brit. a day in June chosen for the observance of the sovereign's birthday. official secrets confidential information involving national security. officialdom n. officialism n. officially adv. [ME (as noun) f. OF f. L officialis (as OFFICE)]

oarfish
oarfish: n. a ribbonfish, Regalecus glesne.

ocarina
ocarina: n. a small egg-shaped ceramic (usu. terracotta) or metal wind instrument. [It. f. oca goose (from its shape)]

object
object: n. & v. --n.
1 a material thing that can be seen or touched.
2 (foll. by of) a person or thing to which action or feeling is directed (the object of attention; the object of our study).
3 a thing sought or aimed at; a purpose.
4 Gram. a noun or its equivalent governed by an active transitive verb or by a preposition.
5 Philos. a thing external to the thinking mind or subject.
6 derog. a person or thing of esp. a pathetic or ridiculous appearance.
7 Computing a package of information and a description of its manipulation. --v.
1 intr. (often foll. by to, against) express or feel opposition, disapproval, or reluctance; protest (I object to being treated like this; objecting against government policies).
2 tr. (foll. by that + clause) state as an objection (objected that they were kept waiting).
3 tr. (foll. by to, against, or that + clause) adduce (a quality or fact) as contrary or damaging (to a case). no object not forming an important or restricting factor (money no object). object-ball Billiards etc. that at which a player aims the cue-ball. object-glass the lens in a telescope etc. nearest to the object observed. object languag.
1 a language described by means of another language (see METALANGUAGE ).
2 Computing a language into which a program is translated by means of a compiler or assembler. object-lesson a striking practical example of some principle. object of the exercise the main point of an activity. objectless adj. objector n. [ME f. med.L objectum thing presented to the mind, past part. of L objicere (as OB-, jacere ject- throw)]

oarlock
oarlock: n. US a rowlock.

observe
observe: v.
1 tr. (often foll. by that, how + clause) perceive, note; take notice of; become conscious of.
2 tr. watch carefully.
3 tr. a follow or adhere to (a law, command, method, principle, etc.). b keep or adhere to (an appointed time). c maintain (silence). d duly perform (a rite). e celebrate (an anniversary).
4 tr. examine and note (phenomena) without the aid of experiment.
5 tr. (often foll. by that + clause) say, esp. by way of comment.
6 intr. (foll. by on) make a remark or remarks about. observable adj. observably adv. [ME f. OF observer f. L observare watch (as OB-, servare keep)]

open
open: adj., v., & n. --adj.
1 not closed or locked or blocked up; allowing entrance or passage or access.
2 a (of a room, field, or other area) having its door or gate in a position allowing access, or part of its confining boundary removed. b (of a container) not fastened or sealed; in a position or with the lid etc. in a position allowing access to the inside part.
3 unenclosed, unconfined, unobstructed (the open road; open views).
4 a uncovered, bare, exposed (open drain; open wound). b Sport (of a goal mouth or other object of attack) unprotected, vulnerable.
5 undisguised, public, manifest; not exclusive or limited (open scandal; open hostilities).
6 expanded, unfolded, or spread out (had the map open on the table).
7 (of a fabric) not close; with gaps or intervals.
8 a (of a person) frank and communicative. b (of the mind) accessible to new ideas; unprejudiced or undecided.
9 a (of an exhibition, shop, etc.) accessible to visitors or customers; ready for business. b (of a meeting) admitting all, not restricted to members etc. 10 a (of a race, competition, scholarship, etc.) unrestricted as to who may compete. b (of a champion, scholar, etc.) having won such a contest. 11 (of government) conducted in an informative manner receptive to enquiry, criticism, etc., from the public. 12 (foll. by to) a willing to receive (is open to offers). b (of a choice, offer, or opportunity) still available (there are three courses open to us). c likely to suffer from or be affected by (open to abuse). 13 a (of the mouth) with lips apart, esp. in surprise or incomprehension. b (of the ears or eyes) eagerly attentive. 14 Mus. a (of a string) allowed to vibrate along its whole length. b (of a pipe) unstopped at each end. c (of a note) sounded from an open string or pipe. 15 (of an electrical circuit) having a break in the conducting path. 16 (of the bowels) not constipated. 17 (of a return ticket) not restricted as to day of travel. 18 (of a cheque) not crossed. 19 (of a boat) without a deck. 20 (of a river or harbour) free of ice. 21 (of the weather or winter) free of frost. 22 Phonet. a (of a vowel) produced with a relatively wide opening of the mouth. b (of a syllable) ending in a vowel. 23 (of a town, city, etc.) not defended even if attacked. --v.
1 tr. & intr. make or become open or more open.
2 a tr. change from a closed or fastened position so as to allow access (opened the door; opened the box). b intr. (of a door, lid, etc.) have its position changed to allow access (the door opened slowly).
3 tr. remove the sealing or fastening element of (a container) to get access to the contents (opened the envelope).
4 intr. (foll. by into, on to, etc.) (of a door, room, etc.) afford access as specified (opened on to a large garden).
5 a tr. start or establish or set going (a business, activity, etc.). b intr. be initiated; make a start (the session opens tomorrow; the story opens with a murder). c tr. (of a counsel in a lawcourt) make a preliminary statement in (a case) before calling witnesses.
6 tr. a spread out or unfold (a map, newspaper, etc.). b (often absol.) refer to the contents of (a book).
7 intr. (often foll. by with) (of a person) begin speaking, writing, etc. (he opened with a warning).
8 intr. (of a prospect) come into view; be revealed.
9 tr. reveal or communicate (one's feelings, intentions, etc.). 10 tr. make (one's mind, heart, etc.) more sympathetic or enlightened. 11 tr. ceremonially declare (a building etc.) to be completed and in use. 12 tr. break up (ground) with a plough etc. 13 tr. cause evacuation of (the bowels). 14 Naut. a tr. get a view of by change of position. b intr. come into full view. --n.
1 (prec. by the) a open space or country or air. b public notice or view; general attention (esp. into the open).
2 an open championship, competition, or scholarship. be open with speak frankly to. keep open house see HOUSE . open air (usu. prec. by the) a free or unenclosed space outdoors. open-air (attrib.) out of doors. open-and-shut (of an argument, case, etc.) straightforward and conclusive. open-armed cordial; warmly receptive. open book a person who is easily understood. open day a day when the public may visit a place normally closed to them. open door free admission of foreign trade and immigrants. open-door adj. open, accessible, public. open the door to see DOOR . open-ended having no predetermined limit or boundary. open a person's eyes see EYE . open-eye.
1 with the eyes open.
2 alert, watchful. open-faced having a frank or ingenuous expression. open-handed generous. open-handedly generously. open-handedness generosity. open-hearted frank and kindly. open-heartedness an open-hearted quality. open-hearth process a process of steel manufacture, using a shallow reverberatory furnace. open-heart surgery surgery with the heart exposed and the blood made to bypass it. open house welcome or hospitality for all visitors. open ice ice through which navigation is possible. open letter a letter, esp. of protest, addressed to an individual and published in a newspaper or journal. open market an unrestricted market with free competition of buyers and sellers. open-minded accessible to new ideas; unprejudiced. open-mindedly in an open-minded manner. open-mindedness the quality of being open-minded. open-mouthed with the mouth open, esp. in surprise. open ou.
1 unfold; spread out.
2 develop, expand.
3 become communicative.
4 accelerate. open-plan (usu. attrib.) (of a house, office, etc.) having large undivided rooms. open prison a prison with the minimum of physical restraints on prisoners. open question a matter on which differences of opinion are legitimate. open-reel (of a tape recorder) having reels of tape requiring individual threading, as distinct from a cassette. open sandwich a sandwich without a top slice of bread. open sea an expanse of sea away from land. open season the season when restrictions on the killing of game etc. are lifted. open secret a supposed secret that is known to many people. open sesame see SESAME . open sho.
1 a business etc. where employees do not have to be members of a trade union (opp. closed shop).
2 this system. open society a society with wide dissemination of information and freedom of belief. Open University (in the UK) a university that teaches mainly by broadcasting and correspondence, and is open to those without formal academic qualifications. open u.
1 unlock (premises).
2 make accessible.
3 reveal; bring to notice.
4 accelerate esp. a motor vehicle.
5 begin shooting or sounding. open verdict a verdict affirming that a crime has been committed but not specifying the criminal or (in case of violent death) the cause. with open arms see ARM(1) ). openable adj. openness n. [OE open]

obtain
obtain: v.
1 tr. acquire, secure; have granted to one.
2 intr. be prevalent or established or in vogue. obtainable adj. obtainability n. obtainer n. obtainment n. obtention n. [ME f. OF obtenir f. L obtinere obtent- keep (as OB-, tenere hold)]

obsolescent
obsolescent: adj. becoming obsolete; going out of use or date. obsolescence n. [L obsolescere obsolescent- (as OB-, solere be accustomed)]

oven
oven: n.
1 an enclosed compartment of brick, stone, or metal for cooking food.
2 a chamber for heating or drying.
3 a small furnace or kiln used in chemistry, metallurgy, etc. oven-ready (of food) prepared before sale so as to be ready for immediate cooking in the oven. [OE ofen f. Gmc]

oriental
oriental: adj. & n. --adj.
1 (often Oriental) a of or characteristic of Eastern civilization etc. b of or concerning the East, esp. E. Asia.
2 (of a pearl etc.) orient. --n. (esp. Oriental) a native of the Orient. orientalism n. orientalist n. orientalize v.intr. & tr. (also -ise). orientally adv. [ME f. OF oriental or L orientalis (as ORIENT)]

obsession
obsession: n.
1 the act of obsessing or the state of being obsessed.
2 a persistent idea or thought dominating a person's mind.
3 a condition in which such ideas are present. obsessional adj. obsessionalism n. obsessionally adv. [L obsessio (as OBSESS)]

obsequious
obsequious: adj. servilely obedient or attentive. obsequiously adv. obsequiousness n. [ME f. L obsequiosus f. obsequium compliance (as OB-, sequi follow)]

organization
organization: n. (also -isation.
1 the act or an instance of organizing; the state of being organized.
2 an organized body, esp. a business, government department, charity, etc.
3 systematic arrangement; tidiness. organization man a man who subordinates his individuality and his personal life to the organization he serves. organizational adj. organizationally adv.

obstetrics
obstetrics: n.pl. (treated as sing.) the branch of medicine and surgery concerned with childbirth and midwifery.

operation
operation: n.
1 a the action or process or method of working or operating. b the state of being active or functioning (not yet in operation). c the scope or range of effectiveness of a thing's activity.
2 an active process; a discharge of a function (the operation of breathing).
3 a piece of work, esp. one in a series (often in pl.: begin operations).
4 an act of surgery performed on a patient.
5 a a strategic movement of troops, ships, etc. for military action. b preceding a code-name (Operation Overlord).
6 a financial transaction.
7 Math. the subjection of a number or quantity or function to a process affecting its value or form, e.g. multiplication, differentiation. operations research = operational research. [ME f. OF f. L operatio -onis (as OPERATE)]

obligatorocean
ocean: n.
1 a a large expanse of sea, esp. each of the main areas called the Atlantic, Pacific, Indian, Arctic, and Antarctic Oceans. b these regarded cumulatively as the body of water surrounding the land of the globe.
2 (usu. prec. by the) the sea.
3 (often in pl.) a very large expanse or quantity of anything (oceans of time). ocean-going (of a ship) able to cross oceans. ocean tramp a merchant ship, esp. a steamer, running on no regular line or route. oceanward adv. (also -wards). [ME f. OF occean f. L oceanus f. Gk okeanos stream encircling the earth's disc, Atlantic]

oesophagus
oesophagus: n. (US esophagus) (pl. oesophagi or -guses) the part of the alimentary canal from the mouth to the stomach; the gullet. oesophageal adj. [ME f. Gk oisophagos]

ovulationobjection
objection: n.
1 an expression or feeling of opposition or disapproval.
2 the act of objecting.
3 an adverse reason or statement. [ME f. OF objection or LL objectio (as OBJECT)]

occiput
occiput: n. the back of the head. occipital adj. [ME f. L occiput (as OB-, caput head)]

oblation
oblation: n. Relig.
1 a thing offered to a divine being.
2 the presentation of bread and wine to God in the Eucharist. oblational adj. oblatory adj. [ME f. OF oblation or LL oblatio (as OBLATE(1))]

obelisk
obelisk: n.
1 a a tapering usu. four-sided stone pillar set up as a monument or landmark etc. b a mountain, tree, etc., of similar shape.
2 = OBELUS. [L obeliscus f. Gk obeliskos dimin. of obelos SPIT(2)]

obstinate
obstinate: adj.
1 stubborn, intractable.
2 firmly adhering to one's chosen course of action or opinion despite dissuasion.
3 inflexible, self-willed.
4 unyielding; not readily responding to treatment etc. obstinacy n. obstinately adv. [ME f. L obstinatus past part. of obstinare persist (as OB-, stare stand)]

odyssey
odyssey: n. (pl. -eys) a series of wanderings; a long adventurous journey. Odyssean adj. [L Odyssea f. Gk Odusseia, title of an epic poem attributed to Homer describing the adventures of Odysseus (Ulysses) on his journey home from Troy]