Etymology: Middle English, from Old English; akin to Old High German offan open, Old English ūp up
Date: before 12th century
1. having no enclosing or confining barrier ; accessible on all or nearly all sides <cattle grazing on an open range> 2. a. (1) being in a position or adjustment to permit passage ; not shut or locked <an open door> (2) having a barrier (as a door) so adjusted as to allow passage <the house was open> b. having the lips parted <stood there with his mouth wide open> c. not buttoned or zipped <an open shirt> 3. a. completely free from concealment ; exposed to general view or knowledge <their hostilities eventually erupted with open war> b. exposed or vulnerable to attack or question ; subject <open to doubt> c. being an operation or surgical procedure in which an incision is made such that the tissues are fully exposed 4. a. not covered with a top, roof, or lid <an open car> <her eyes were open> b. having no protective covering <open wiring> <an open wound> 5. not restricted to a particular group or category of participants <open to the public> <open housing>: as a. enterable by both amateur and professional contestants <an open tournament> b. enterable by a registered voter regardless of political affiliation <an open primary> 6. fit to be traveled over ; presenting no obstacle to passage or view <the open road> <open country> 7. having the parts or surfaces laid out in an expanded position ; spread out ; unfolded <an open book> 8. a. (1) low 13 (2) formed with the tongue in a lower position <Italian has an open and a close e> b. (1) having clarity and resonance unimpaired by undue tension or constriction of the throat <an open vocal tone> (2) of a tone produced by an open string or on a wind instrument by the lip without the use of slides, valves, or keys 9. a. available to follow or make use of <the only course open to us> b. not taken up with duties or engagements <keep an hour open on Friday> c. not finally decided ; subject to further consideration <the salary is open> <an open question> d. available for a qualified applicant ; vacant <the job is still open> e. remaining available for use or filling until canceled <an open order for more items> f. available for future purchase <these items are in open stock> g. available for breeding ; not now pregnant <an open heifer> h. not proprietary ; available to third party developers <open source code> 10. a. characterized by ready accessibility and usually generous attitude: as (1) generous in giving (2) willing to hear and consider or to accept and deal with ; responsive (3) free from reserve or pretense ; frank b. accessible to the influx of new factors (as foreign goods) <an open market> 11. a. having openings, interruptions, or spaces <open mesh>: as (1) being porous and friable <open soil> (2) sparsely distributed ; scattered <open population> (3) of a compound having components separated by a space in writing or printing (as opaque projector) b. not made up of a continuous closed circuit of channels <the insect circulatory system is open> 12. a. of an organ pipe not stopped at the top b. of a string on a musical instrument not stopped by the finger 13. being in operation <an open microphone>; especially ready for business, patronage, or use <the store is open from 9 to 5> <the new highway will be open next week> 14. a. (1) characterized by lack of effective regulation of various commercial enterprises <an open town> (2) not repressed by legal controls <open gambling> b. free from checking or hampering restraints <an open economy> c. relatively unguarded by opponents <passed to an open teammate> 15. having been opened by a first ante, bet, or bid <the bidding is open> 16. of punctuation characterized by sparing use especially of the comma 17. a. containing none of its endpoints <an open interval> b. being a set or composed of sets each point of which has a neighborhood all of whose points are contained in the set <the interior of a sphere is an open set> 18. a. being an incomplete electrical circuit b. not allowing the flow of electricity <an open switch> 19. of a universe having insufficient mass to halt expansion gravitationally Synonyms: see frank, liable • open adverb • openly adverb • openness noun II. verb (opened; opening) Date: before 12th century transitive verb 1. a. to move (as a door) from a closed position b. to make available for entry or passage by turning back (as a barrier) or removing (as a cover or an obstruction) 2. a. to make available for or active in a regular function <open a new store> b. to make accessible for a particular purpose <opened new land for settlement> <open the way for changes> c. to initiate access to (a computer file) prior to use 3. a. to disclose or expose to view ; reveal b. to make more discerning or responsive ; enlighten <must open our minds to the problems> c. to bring into view or come in sight of by changing position 4. a. to make an opening in <opened the boil> b. to loosen and make less compact <open the soil> 5. to spread out ; unfold <opened the book> 6. a. to enter upon ; begin <opened the meeting> b. to commence action in a card game by making (a first bid), putting a first bet in (the pot), or playing (a card or suit) as first lead 7. to restore or recall (as an order) from a finally determined state to a state in which the parties are free to prosecute or oppose intransitive verb 1. to become open <the office opened early> 2. a. to spread out ; expand <the wound opened under the strain> b. to become disclosed <a beautiful vista opened before us> 3. to become enlightened or responsive 4. to give access <the rooms open onto a hall> 5. speak out 2 <finally he opened freely on the subject> 6. a. to begin a course or activity <the play opens on Tuesday> b. to make a bet, bid, or lead in commencing a round or hand of a card game 7. to provide the opening performance of a show before the main event • openability noun • openable adjective III. noun Date: 13th century 1. opening 2. open and unobstructed space: as a. open air b. open water 3. an open contest, competition, or tournament 4. a public or unconcealed state or position
New Collegiate Dictionary. 2001.