n.

1. a clear or unobstructed space or expanse of land or water;
   clear
   
   • finally broke out of the forest into the open
2. where the air is unconfined;
   outdoors, out-of-doors, open air
   
   • he wanted to get outdoors a little
   • the concert was held in the open air
   • camping in the open
3. a tournament in which both professionals and amateurs may play
4. information that has become public;
   surface
   
   • all the reports were out in the open
   • the facts had been brought to the surface

v.

1. cause to open or to become open;
   open up
   
   • Mary opened the car door
2. start to operate or function or cause to start operating or functioning;
   open up
   
   • open a business
3. become open;
   open up
   
   • The door opened
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;
   unfold, spread, spread out
   
   • open the map
   • spread your arms
6. make available;
   open up
   
   • This opens up new possibilities
7. become available;
   open up
   
   • an opportunity opened up
8. have an opening or passage or outlet
   
   • The bedrooms open into the hall
9. make the opening move
   
   • Kasparov opened with a standard opening
10. afford access to;
    afford, give
    
    • the door opens to the patio
    • The French doors give onto a terrace
11. display the contents of a file or start an application as on a computer

adj.

1. affording unobstructed entrance and exit; not shut or closed;
   unfastened
   
   • an open door
   • they left the door open
2. affording free passage or access
   
   • open drains
   • the road is open to traffic
   • open ranks
3. with no protection or shield;
   exposed
   
   • the exposed northeast frontier
   • open to the weather
   • an open wound
4. open to or in view of all
   
   • an open protest
   • an open letter to the editor
5. used of mouth or eyes;
   opened
   
   • keep your eyes open
   • his mouth slightly opened
6. not having been filled
   
   • the job is still open
7. accessible to all
   
   • open season
   • an open economy
8. not defended or capable of being defended;
   assailable, undefendable, undefended
   
   • an open city
   • open to attack
9. (of textures) full of small openings or gaps;
   loose
   
   • an open texture
   • a loose weave
10. having no protecting cover or enclosure
    
    • an open boat
    • an open fire
    • open sports cars
11. (set theory) of an interval that contains neither of its endpoints
12. not brought to a conclusion; subject to further thought;
    undecided, undetermined, unresolved
    
    • an open question
    • our position on this bill is still undecided
    • our lawsuit is still undetermined
13. not sealed or having been unsealed;
    opened
    
    • the letter was already open
    • the opened package lay on the table
14. without undue constriction as from e.g. tenseness or inhibition
    
    • the clarity and resonance of an open tone
    • her natural and open response
15. ready or willing to receive favorably;
    receptive
    
    • receptive to the proposals
16. open and observable; not secret or hidden;
    overt
    
    • an overt lie
    • overt hostility
    • overt intelligence gathering
    • open ballots
17. not requiring union membership;
    open(a)
    
    • an open shop employs nonunion workers
18. possibly accepting or permitting;
    capable, subject
    
    • a passage capable of misinterpretation
    • open to interpretation
    • an issue open to question
    • the time is fixed by the director and players and therefore subject to much variation
19. affording free passage or view;
    clear
    
    • a clear view
    • a clear path to victory
    • open waters
    • the open countryside
20. openly straightforward and direct without reserve or secretiveness;
    candid, heart-to-heart
    
    • his candid eyes
    • an open and trusting nature
    • a heart-to-heart talk
21. ready for business
    
    • the stores are open