1. Affording unobstructed entrance and exit; not shut or closed
   "they left the door open"; "an open door";
   - unfastened
    
2. Affording free passage or access
   "open ranks"; "open drains"; "the road is open to traffic"
    
3. Available to or viewable by the public
   "an open protest"; "an open letter to the editor"
    
4. With no protection or shield
   "open to the weather"; "an open wound";
   - exposed
    
5. Accessible to all
   "open season"; "an open economy"
    
6. Openly straightforward and direct without reserve or secretiveness
   "an open and trusting nature";
   - candid, heart-to-heart
    
7. Observable; not secret or hidden
   "open ballots";
   - overt
    
8. Used of mouth or eyes
   "keep your eyes open";
   - opened
    
9. Not brought to a conclusion; subject to further thought
   "an open question";
   - undecided, undetermined, unresolved
    
10. Not having been filled
    "the job is still open"
     
11. Not sealed or having been unsealed
    "the letter was already open";
    - opened
     
12. Without undue constriction as from e.g. tenseness or inhibition
    "the clarity and resonance of an open tone"; "her natural and open response"
     
13. Ready or willing to receive favourably
    "open to the proposals";
    - receptive
     
14. Not defended or capable of being defended
    "an open city"; "open to attack";
    - assailable, undefendable, undefended
     
15. (of textures) full of small openings or gaps
    "an open texture";
    - loose
     
16. Having no protecting cover or enclosure
    "open sports cars"; "an open boat"; "an open fire"
     
17. Not requiring union membership
    "an open shop employs nonunion workers"
     
18. Accepting, susceptible, or vulnerable to something specified
    "open to interpretation"; "an issue open to question";
    - capable, subject
     
19. Affording free passage or view
    "open waters"; "the open countryside";
    - clear
     
20. (set theory) of an interval that contains neither of its endpoints
    "The open interval (0, 1) includes all numbers greater than 0 and less than 1, but not 0 or 1 themselves"

1. Cause to allow entrance or exit; allow entry after being shut
   "Mary opened the car door";
   - open up
    
2. Become open
   "The door opened"; "The flower opened up in the morning sun";
   - open up
    
3. Start to operate or function or cause to start operating or functioning
   "open a business"; "The new store will open up next week";
   - open up
    
4. Begin or set in action, of meetings, speeches, recitals, etc.
   "He opened the meeting with a long speech"
    
5. Spread out or open from a closed or folded state
   "open the map";
   - unfold, spread, spread out
    
6. Make available
   "This opens up new possibilities";
   - open up
    
7. Become available
   "an opportunity opened up";
   - open up
    
8. Provide entry or access to
   "The bedrooms open into the hall"
    
9. Display the contents of a file or start an application as on a computer
   "She opened the document on her laptop"; "He opened the web browser"
    
10. (chess) make the opening move
    "Kasparov opened with a standard opening"

1. A clear or unobstructed space or expanse of land or water
   "finally broke out of the forest into the open";
   - clear
    
2. Where the air is unconfined
   "the concert was held in the open air"; "camping in the open";
   - outdoors, out-of-doors, open air
    
3. A tournament in which both professionals and amateurs may play
   "The U.S. Open golf tournament attracts top players from around the world"
    
4. Information that has become public
   "all the reports were out in the open";
   - surface

Derived forms: opened, opens, opener, openest, opening

See also: acceptant, acceptive, admissive, agape, agaze, ajar, artless, assimilative, available, bald, barefaced, coarse, explicit, expressed, gaping, harsh, hospitable, ingenuous, naked, nonunion, opened, out on a limb, pioneer, public, raw, staring, susceptible, unconcealed, unconstricted, undisguised, unenclosed, unobstructed, unprotected, unrestricted, unsealed, unsettled, unstoppered, visible, vulnerable, wide, wide-eyed, wide-open, yawning

Type of: afford, alter, area, arise, be, begin, change, change state, come up, commence, country, display, embark on, exhibit, exist, expose, exterior, general knowledge, get, get down, give, go, modify, move, outside, public knowledge, set about, set out, start, start out, start up, tournament, tourney [N. Amer], turn, undo, yield

Antonym: close, close up, closed, covert, fold, unopen [rare], unreceptive

Encyclopedia: Open, closed, open