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o·pen (ōpən)
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adj.
1.
a. Affording unobstructed entrance and exit; not shut or closed.
b. Affording unobstructed passage or view: open waters; the open countryside.
2.
a. Having no protecting or concealing cover: an open wound; an open sports car.
b. Completely obvious; blatant: open disregard of the law.
c. Carried on in full view of others; not hidden or private: open warfare; open family strife.
d. Sports Not defended or not closely defended by an opponent: an open goal; an open receiver.
3.
a. Not sealed or tied: an open envelope.
b. Spread out; unfolded: an open book.
4. Having interspersed gaps, spaces, or intervals: open ranks; an open weave.
5.
a. Accessible to all; unrestricted as to participants: an open competition.
b. Free from limitations, boundaries, or restrictions: open registration.
c. Enterable by registered voters regardless of political affiliation: an open primary.
d. Computers Of or relating to a file that can be accessed.
6.
a. Lacking effective regulation: an open town in which gambling predominated.
b. Not legally repressed: open drug trafficking.
7.
a. Susceptible; vulnerable: open to interpretation; an issue that is open to question.
b. Willing to consider or deal with something: open to suggestions.
8.
a. Available; obtainable: The job is still open.
b. Available for use: an open account; the only course open to us.
9. Ready to transact business: The store is open.
10. Not engaged or filled: has an open hour for emergency cases.
11. Not yet decided; subject to further thought: an open question.
12.
a. Characterized by lack of secrecy or reserve; candid: Please be open with me. See Synonyms at frank1.
b. Free of prejudice; receptive to new ideas and arguments: She listened to the proposal with an open mind.
c. Generous: He is very open with his time.
13. Printing
a. Widely spaced or leaded. Used of typeset or other printed matter.
b. Having constituent elements separated by a space in writing or printing: The word sea lion is an open compound.
14. Music
a. Not stopped by a finger. Used of a string or hole of an instrument.
b. Produced by an unstopped string or hole or without the use of slides, valves, or keys: an open note on a trumpet.
c. Played without a mute: an open wind instrument.
15. Linguistics
a. Articulated with the tongue in a low position, as the vowel in far.
b. Ending in a vowel or diphthong: an open syllable.
16. Designating a method of punctuation in which commas and other marks are used sparingly.
17. Being in operation; live: an open microphone.
18. New England Clear. Used of weather. fair1
19. Electricity Containing a gap across which electricity cannot pass: an open circuit.
20. Mathematics
a. Of or relating to an interval containing neither of its endpoints.
b. Of or being a set such that at least one neighborhood of every point in the set is within the set.
c. Of or being a set that is the complement of a closed set.
21. Sports
a. Having the forward foot farther from the intended point of impact with the ball than the rear foot: an open batting stance.
b. Held or swung with the top or outer edge of the striking face pointing slightly farther away from the objective than the lower or inner edge: The club struck the ball with an open face, causing a slice.
22. Physics
a. Of or relating to an open system.
b. Of or relating to an open universe.
v. o·pened, o·pen·ing, o·pens
v.tr.
1.
a. To make no longer closed or fastened: open a window.
b. To remove obstructions from; clear: open a drain.
2.
a. To make or force an opening in: The surgeon opened the patient's chest.
b. To make (a hole or gap) in something: opened a hole in the levee.
c. To form spaces or gaps between: soldiers opening ranks.
d. To break the continuity of; make a gap in: open a circuit.
3.
a. To remove the cover, cork, or lid from: open a jar.
b. To remove the wrapping from: open a package.
4.
a. To move apart or unfold so that the inner parts are displayed; spread out: open a newspaper; open a book.
b. To part the lids or lips of: Open your eyes. Open your mouth.
5.
a. To begin or form the start of; initiate: The scene that opens the novel.
b. To begin the operation of: open a new business.
c. To begin (the action in a game of cards) by making the first bid, placing the first bet, or playing the first lead.
6. To make available for use: opened the area to commercial development; opened the computer file and retrieved some data.
7. To make more responsive, understanding, or generous: a question that opened his mind to a different way of looking at the problem.
8. To make known to the public: opened the formerly classified files to reporters.
9. Sports To modify (one's stance), as in baseball or golf, so that it is open.
10.
a. To perform as the first act of (a concert, for example): An up-and-coming rock group opened the music festival.
b. To perform prior to the main act of (a concert, for example): Two different bands opened the concert on Friday night.
v.intr.
1. To become no longer closed or fastened: The door opened slowly.
2. To draw apart; separate: The wound opened under pressure.
3. To spread apart; unfold: The tulips opened.
4. To come into view; become revealed: The plain opened before us.
5. To become responsive, understanding, or generous: His heart finally opened, and he understood her disappointment.
6.
a. To be or serve as a beginning; commence: The meeting opened with a call to order.
b. To give an initial statement in a trial.
c. To begin business or operation: The store opens early on Saturday.
d. To be performed, shown, or made available to the public for the first time: The play opens next week.
e. To be priced or listed at a specified amount when trading begins: Shares opened high and fell sharply.
f. To make a bid, bet, or lead in starting a game of cards.
7. To give access: The room opens onto a terrace.
8.
a. To perform as the first act of a multi-act performance: The singer was nervous to open for so many talented musicians.
b. To perform prior to the main act of a multi-act performance: The young comedians were thrilled to open for such a well-known standup comic.
n.
1. An unobstructed area of land or water: sailed out of the harbor into the open.
2. The outdoors: camping in the open.
3. An undisguised or unconcealed state: brought the problem out into the open.
4. A tournament or contest in which both professional and amateur players may participate.
5. A beginning: Shares were down at the market open.
Phrasal Verb:
open up
1. To spread out; unfold: A green valley opened up before us.
2. To begin operation or start (something): The new store opens up next month. The band opened up the concert with an old favorite.
3. To begin firing: The artillery opened up at dawn.
4. Informal To speak freely and candidly: At last the frightened witness opened up and told the truth.
5. To make an opening in by cutting: The surgeon opened up the patient's chest.
6. To make available or accessible: open up new markets.
7. Informal To accelerate. Used of a motor vehicle.
8. Sports To get a sudden, insurmountable lead in (an athletic contest).
Idioms:
open fire
To begin firing a gun or guns.
open (one's) eyes
To become aware of the truth of a situation.

[Middle English, from Old English; see upo in the Appendix of Indo-European roots.]

open·ly adv.
open·ness n.

The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2017 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
 

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