o·pen / ˈōpən/ • adj. 1. allowing access, passage, or a view through an empty space; not closed or blocked up: it was a warm evening and the window was open the door was wide open. ∎  (of a container) not fastened or sealed; in a position or with the lid or other covering in a position allowing access to the inside part or the contents: the case burst open and its contents flew all over the place. ∎  (of a garment or its fasteners) not buttoned or fastened: his tie was knotted below the open collar of his shirt. ∎  (of the mouth or eyes) with lips or lids parted: his eyes were open but he could see nothing. ∎  free from obstructions: the pass is kept open all year by snowplows. ∎ inf. (of a car or house) unlocked. ∎ Phonet. (of a vowel) produced with a relatively wide opening of the mouth and the tongue kept low. ∎ Phonet. (of a syllable) ending in a vowel. ∎  (of the bowels) not constipated. ∎  (of a game or style of play) characterized by action that is spread out over the field.2. exposed to the air or to view; not covered: an open fire burned in the grate. ∎  (of an area of land) not covered with buildings or trees: increasing numbers of new houses in open countryside. ∎  having spaces or gaps between elements: air circulates more readily through an open tree. ∎  (of a fabric) loosely knitted or woven. ∎  (of a team member in a game) unguarded and therefore able to receive a pass: the trick is spreading the defense so that at least one receiver gets open. ∎  (of a goalmouth or other object of attack in a game) unprotected; vulnerable. ∎  (of a boat) without a deck: days without food and water in an open boat. ∎  (open to) likely to suffer from or be affected by; vulnerable or subject to: the system is open to abuse. ∎  (of a town or city) officially declared to be undefended, and so immune under international law from bombardment. ∎  with the outer edges or sides drawn away from each other; unfolded: the trees had buds and a few open flowers. ∎  (of a book or file) with the covers parted or the contents in view, allowing it to be read: she was copying verses from an open Bible | fig. her mind was an open book to him. ∎  (of a hand) not clenched into a fist. ∎  damaged or injured by a deep cut in the surface: he had his arm slashed open.3. (of a store, place of entertainment, etc.) officially admitting customers or visitors; available for business: the store stays open until 9 p.m. ∎  (of a bank account) available for transactions: the minimum required to keep the account open. ∎  (of a telephone line) ready to take calls: our free advice line is open from 8:30 to 5:30. ∎  (of a choice, offer, or opportunity) still available; such that people can take advantage of it: the offer is open while supplies last we need to consider what options are left open.4. (of a person) frank and communicative; not given to deception or concealment: she was open and naive I was quite open about my views. ∎  not concealed; manifest: his eyes showed open admiration. ∎  (of conflict) fully developed and unconcealed: the dispute erupted into open war. ∎  involving no concealment, restraint, or deception; welcoming discussion, criticism, and inquiry: the conclusions were reached in open discussion.5. (of a question, case, or decision) not finally settled; still admitting of debate: students' choice of major can be kept open until the second year. ∎  (of the mind) accessible to new ideas; unprejudiced: I'm keeping an open mind about my future. ∎  (open to) receptive to: the union was open to suggestions for improvements. ∎  (open to) admitting of; making possible: the message is open to different interpretations. ∎  freely available or accessible; offered without restriction: the service is open to all students at the university. ∎  with no restrictions on those allowed to attend or participate: an open audition was announced. ∎  (also Open) (of an award or the competition for it) unrestricted as to who may qualify to compete: each horse had won two open races. ∎  (of a ticket) not restricted as to day of travel.6. Mus. (of a string) allowed to vibrate along its whole length. ∎  (of a pipe) unstopped at each end. ∎  (of a note) sounded from an open string or pipe.7. (of an electrical circuit) having a break in the conducting path.8. Math. (of a set) not containing any of its limit points.• v. [tr.] 1. move or adjust (a door or window) so as to leave a space allowing access and view: she opened the door and went in | [intr.] “Open up!” he said. ∎  [intr.] (of a door or window) be moved or adjusted to leave a space allowing access and view: the door opened and a man came out. ∎  undo or remove the lid, cover, or fastener of (a container) to get access to the contents: he opened a bottle inexpertly, spilling some of the wine. ∎  remove the covers or wrapping from: can we open the presents now? ∎  part the lips or lids of (a mouth or eye): she opened her mouth to argue. ∎  [intr.] (of the mouth or eyes) have the lips or lids parted in this way: her eyes slowly opened. ∎  (of a wound) lose or lack its protective covering: old wounds opened and I bled a little bit. ∎  improve or make possible access to or passage through: the president announced that his government would open the border. ∎  cause evacuation of (the bowels). ∎  [intr.] (open onto/into) (of a room, door, or window) give access to: beautiful French doors that opened onto a balcony. ∎  [intr.] (of a panorama) come into view; spread out before someone: stop to marvel at the views that open out below. ∎  Naut. achieve a clear view of (a place) by sailing past a headland or other obstruction: we shall open Simon's Bay at any minute now.2. spread out; unfold: the eagle opened its wings and circled up into the air the tail looks like a fan when it is opened out fully. ∎  [intr.] be unfolded; spread out to the full extent: the flowers never opened beyond narrow points. ∎  increase the spaces or gaps between elements of (something): spacing the scaffolds opens up the tree so light can penetrate. ∎  part the covers or display the contents of (a book or file) to read it: she opened her book at the prologue. ∎  [intr.] (open out) become wider or more spacious: the path opened out into a glade.3. allow public access to: one woman raised $731 by opening her home and selling coffee and tea. ∎  make available: the new plan proposed to open up opportunities to immigrants. ∎  make more widely known; reveal: the move may force the company to open up its plans for the future. ∎  [intr.] (open up) become more communicative or confiding: neither one of them had opened up to me about their troubles. ∎  make (one's mind or heart) more receptive or sympathetic: open your mind to what is going on around you. ∎  (open someone (up) to) make someone vulnerable to: the process is going to open them to a legal threat.4. establish (a new business, movement, or enterprise): they have opened a new restaurant across the street. ∎  [intr.] (of an enterprise, esp. a commercial one) be established: two new restaurants open this week. ∎  [intr.] (of a store, place of entertainment, etc.) be officially ready to receive customers or visitors; become ready for business: the mall didn't open until 10. ∎  take the action required to make ready for use: they have the $10 necessary to open a savings account click twice to open a file. ∎  [intr.] (of a meeting or a sporting or artistic event) formally begin: the incident occurred just before the Olympic Games were due to open. ∎  [intr.] (of a piece of writing or music) begin: the chapter opens with a discussion of Anglo-American relations. ∎  (open up) [intr.] (of a process) start to develop: a new and dramatic phase was opening up. ∎  officially or ceremonially declare (a building, road, etc.) to be completed and ready for use: we will have to wait until a new bypass is opened before we can tackle the problem of congestion. ∎  (of a counsel in a court of law) make a preliminary statement in (a case) before calling witnesses. ∎  [tr.] Bridge make (the first bid) in the auction.5. break the conducting path of (an electrical circuit): the switch opens the motor circuit. ∎  [intr.] (of an electrical circuit or device) suffer a break in its conducting path.• n. 1. (Open) a championship or competition with no restrictions on who may qualify to compete: the venue for the British Open.2. an accidental break in the conducting path for an electrical current.PHRASES: be open with speak frankly to; conceal nothing from: I had always been completely open with my mother.in (or into) the open out of doors; not under cover. ∎  not subject to concealment or obfuscation; made public: we have never let our dislike for him come into the open.in open court in a court of law, before the judge and the public.open-and-shut (of a case or argument) admitting no doubt or dispute; straightforward.open the door to see door.open someone's eyes see eye.open fire begin to shoot a weapon.an open mind see mind.with one's eyes open (or with open eyes) fully aware of the risks and other implications of an action or situation: I went into the job with my eyes open.with open arms see arm¹ .PHRASAL VERBS: open up begin shooting: the enemy artillery had opened up.open something up1. accelerate a motor vehicle.2. (of an athlete or team) create an advantage for one's side: he opened up a lead of 14–8.DERIVATIVES: o·pen·a·ble adj.o·pen·ness n.

open open sesame in the tale of Ali Baba and the Forty Thieves, the magic words by which the door of the robbers' cave was made to fly open; the phrase is thus used for a means of securing access to what would normally be inaccessible.

See also a door must be either shut or open, leave the door open, a golden key can open any door.

OPEN

To make accessible, visible, or available; to submit to review, examination, or inquiry through the elimination of restrictions or impediments.

To open a judgment means to render it capable of reexamination by removing or relaxing the bar of its finality. A judgment is ordinarily opened at the insistence of a party who is able to show good cause as to why the execution of the judgment would be inequitable.

To open a court is to formally announce, ordinarily through the bailiff, that the session has commenced and that the business before the tribunal will proceed.

The term open is also used as an adjective in reference to that which is patent, visible, apparent, or notorious, such as a defect in a product, or conduct such as lewdness.

open To instruct an application that a particular file is required for reading, writing, or both. When a file is opened, its name is passed to the operating system, which locates it and checks that it exists and is available – creating it if necessary – before giving to the application status information and the location of the first record. Once a file has been opened for writing it is normally unavailable to other applications until it has been closed (but see record locking).

open not shut, confined, or covered (with many fig. uses). OE. open = OS. opan (Du. open), OHG. offan (G. offen), ON. opinn :- Gmc. *upanaz, having the form of a strong pp. (see -EN6) f. UP, as if meaning ‘put or set up’.
Hence open vb. OE. openian = OS. opanon (Du. openen), OHG. offanōn (G. öffnen).