not closed or barred at the time, as a doorway by a door, a window by a sash, or a gateway by a gate

to leave the windows open at night.

(of a door, gate, window sash, or the like) set so as to permit passage through the opening it can be used to close.

having no means of closing or barring

an open portico.

having the interior immediately accessible, as a box with the lid raised or a drawer that is pulled out.

relatively free of obstructions to sight, movement, or internal arrangement

an open floor plan.

constructed so as to be without cover or enclosure on the top or on some or all sides

an open boat.

having relatively large or numerous spaces, voids, or intervals

an open architectural screen; open ranks of soldiers.

perforated or porous

an open texture.

relatively unoccupied by buildings, fences, trees, etc.

open country.

not covered or closed; with certain parts apart

open eyes; open mouth.

without a covering, esp. a protective covering; unprotected; unenclosed; exposed

an open wound; open electrical wires.

extended or unfolded

an open newspaper.

without restrictions as to who may participate

an open competition; an open session.

accessible or available to follow

the only course still open to us.

not taken or filled; not preempted; available; vacant

Which job is open?

ready for or carrying on normal trade or business

The new store is now open. The office is open on Saturdays.

not engaged or committed

Have you any open time on Monday?

accessible, as to appeals, ideas, or offers

to be open to suggestion.

exposed to general view or knowledge; existing, carried on, etc., without concealment

open disregard of the rules.

acting publicly or without concealment, as a person.

unreserved, candid, or frank, as persons or their speech, aspect, etc.

an open manner.

generous, liberal, or bounteous

to give with an open hand.

liable or subject

open to question; open to retaliation.

undecided; unsettled

several open questions.

without effective or enforced legal, commercial, or moral regulations

an open town.

unguarded by an opponent

an open wide receiver.

noting the part of the sea beyond headlands or enclosing areas of land

to sail on the open seas.

free of ice, as a body of water or a seaport.

free of navigational hazards

an open coast.

(of a seaport) available for foreign trade; not closed by government regulations or by considerations of health.

(of a microphone) in operation; live.

(of a delimiting punctuation mark) occurring at the beginning of a group of words or characters that is set off, as from surrounding text

open parenthesis; open quotes. Compare close def. 51

not yet balanced or adjusted, as an account.

not constipated, as the bowels.

Phonetics .

(of a vowel) articulated with a relatively large opening above the tongue or with a relatively large oral aperture, as the vowel sound of cot compared with that in caught.

(of a syllable) ending with a vowel.

(of a consonant) continuant ( opposed to stopped ).

Linguistics . (of a class of items) readily admitting new members, as the class of nouns, verbs, or adjectives ( opposed to closed ).

Printing .

(of type) in outline form.

widely spaced or leaded, as printed matter.

Music .

(of an organ pipe) not closed at the far end.

(of a string) not stopped by a finger.

(of a note) produced by such a pipe or string or, on a wind instrument, without the aid of a slide, key, etc.

Mathematics .

(of an interval) containing neither endpoint.

(of a set) consisting of points having neighborhoods wholly contained in the set, as the set of points within a circle.

(of a map from one topological space to another) having the property that the image of an open set is an open set.

free from frost; mild or moderate

an open winter.

Animal Husbandry . (of a female animal) not pregnant.

Textiles . (of a fabric or weave) so loosely woven that spaces are visible between warp and filling yarns.

to move (a door, window sash, etc.) from a shut or closed position so as to admit of passage.

to render (a doorway, gateway, window, etc.) unobstructed by moving a door, window sash, etc., away from it.

to render the interior of (a box, drawer, etc.) readily accessible.

to clear (a passage, channel, etc.) of obstructions.

to clear (areas or passages in the body).

to give access to; make accessible or available, as for use

to open a port for trade.

to establish for business purposes or for public use

to open an office.

to set in action, begin, start, or commence (sometimes fol. by up )

to open a campaign.

to uncover, lay bare, or expose to view.

to expand, unfold, or spread out

to open a map.

to make less compact, less closely spaced, or the like

to open ranks.

to disclose, reveal, or divulge.

to render accessible to knowledge, enlightenment, sympathy, etc.

to open one's mind.

to cut, blast, or break into

to open a safe with nitro.

to make or produce (an opening) by cutting or breaking, or by pushing aside or removing obstructions

to open a way through a crowd.

to make an incision or opening in

to open a boil.

Law .

to recall or revoke (a judgment, decree, etc.) for the purpose of allowing further contest or delay.

to make the first statement of (a case) to the court or jury.

Cards . to begin a hand by making (the first bid), placing (the first bet), or playing (a given card or suit) as the lead.

Nautical . to sail (a course) so that the apparent location of a distant fixed object changes with relation to a nearer fixed object (sometimes fol. by out ).

to become open, as a door, building, box, or enclosure.

to afford access

a door that opens into a garden.

to have an opening, passage, or outlet

The room opens into a corridor.

(of a building, theater, etc.) to open its doors to the public

The museum opens at one o'clock.

to begin a session or term, as a school.

to begin a season, series of performances, or tour, as a theatrical company

The play will open in Boston.

to begin, start, or commence an activity

The game opened with the national anthem.

to part, or seem to part, so as to allow or reveal a passage

At last the cliffs opened to show us that we were heading for the sea.

to become disclosed or revealed.

to come into view; become more visible or plain.

to become receptive to knowledge, sympathy, etc., as the mind.

to disclose or reveal one's knowledge, thoughts, feelings, etc.

to unfold or expand, as a blossom, so as to reveal the interior.

to spread out or expand, as the hand or a fan.

to spread apart or separate, as pages of a book, newspaper, etc.

Open to page 32.

to spread or come apart; burst

The wound opened.

to become less compact, less closely spaced, or the like

The ranks began to open.

Cards . to make the first bet, bid, or lead in beginning a hand.

Hunting . (of hounds) to begin to bark, as on the scent of game.

an open or clear space.

the open air.

the open water, as of the sea.

an opening or aperture.

an opening or opportunity.

a contest or tournament in which both amateurs and professionals may compete, esp. in golf and tennis.

the open,

the unenclosed or unobstructed country.

the outdoors

Vacations in the open are fine for the entire family.

the condition of being unconcealed, recognized, or publicly known

The scandal is now out in the open.

open up,

to become or make open.

to expand, esp. before the eye

A breathtaking panorama opened up as we reached the top of the hill.

to achieve the initial development of

to open up a business office; to open up trade with China.

Slang . to increase speed or the speed of (a vehicle).

adjective

closed , fastened , locked , shut , blocked , inaccessible , obstructed , unavailable , ambiguous , deceitful , unclear , vague , certain , decided , definite , sure , deceptive , dishonest , lying , shifty , subjective

verb

close , conclude , end , finish , shut , block , bury , cover , exclude , hide , hinder

adjective

accessible , agape , airy , ajar , bare , clear , cleared , dehiscent , disclosed , emptied , expanded , expansive , exposed , extended , extensive , free , gaping , made passable , naked , navigable , passable , patent , patulous , peeled , removed , rent , revealed , ringent , rolling , spacious , spread out , stripped , susceptible , unbarred , unblocked , unbolted , unburdened , uncluttered , uncovered , unfolded , unfurled , unimpeded , unlocked , unobstructed , unplugged , unsealed , unshut , unstopped , vacated , wide , yawning , admissible , agreeable , allowable , approachable , appropriate , attainable , available , employable , fit , general , getable , nondiscriminatory , not posted , obtainable , on deck , on tap * , open-door , operative , permitted , practicable , proper , public , reachable , securable , suitable , to be had , unconditional , unoccupied , unqualified , unrestricted , usable , vacant , welcoming , within reach , apparent , avowed , barefaced , blatant , conspicuous , downright , evident , flagrant , frank , manifest , noticeable , overt , plain , unconcealed , undisguised , visible , well-known , ambiguous , arguable , controversial , debatable , doubtful , dubious , dubitable , equivocal , indecisive , in question , moot , problematic , questionable , uncertain , unresolved , unsettled , up for discussion , up in the air , yet to be decided , artless , candid , disinterested , fair , guileless , impartial , ingenuous , innocent , lay it on the line , mellow , natural , objective , on the level * , open-and-shut * , openhearted * , receptive , sincere , straightforward , talking turkey , transparent , unbiased , uncommitted , undissembled , unprejudiced , unreserved , up-front , unprotected , prone , subject , susceptive , vulnerable , acceptant , amenable , open-minded , responsive , operable , utilizable , uninhabited , undecided , undetermined , unsure , vague , direct , forthright , honest , man-to-man , plainspoken , straight , straight-out

verb

begin business , bow , commence , convene , embark , get things rolling , inaugurate , initiate , jump , kick off , launch , meet , raise the curtain * , ring in , set in motion , set up shop , sit , start , start the ball rolling , bare , break in , break out , broach , burst , bust in , come apart , crack , disclose , display , disrupt , expand , fissure , free , gap , gape , hole , jimmy , kick in , lacerate , lance , penetrate , perforate , pierce , pop , puncture , release , reveal , rupture , separate , sever , slit , slot , split , tap , throw wide , unbar , unblock , unbolt , unclose , unclothe , uncork , uncover , undo , unfasten , unfold , unfurl , unlatch , unlock , unroll , unseal , unshut , unstop , untie , unwrap , vent , ventilate , yawn , yawp , extend , fan , outstretch , stretch , approach , begin , enter , get off , institute , lead off , set about , set out , set to , take on , take up , undertake