n.

1. an open or empty space in or between things;
   gap
   
   • there was a small opening between the trees
   • the explosion made a gap in the wall
2. a ceremony accompanying the start of some enterprise
3. becoming open or being made open
   
   • the opening of his arms was the sign I was waiting for
4. the first performance (as of a theatrical production);
   opening night, curtain raising
   
   • the opening received good critical reviews
5. the act of opening something
   
   • the ray of light revealed his cautious opening of the door
6. opportunity especially for employment or promotion
   
   • there is an opening in the sales department
7. the initial part of the introduction
   
   • the opening established the basic theme
8. a possible alternative;
   possibility, possible action
   
   • bankruptcy is always a possibility
9. an aperture or hole that opens into a bodily cavity;
   orifice, porta
   
   • the orifice into the aorta from the lower left chamber of the heart
10. a vacant or unobstructed space that is man-made
    
    • they left a small opening for the cat at the bottom of the door
11. an entrance equipped with a hatch; especially a passageway between decks of a ship;
    hatchway, scuttle
12. a recognized sequence of moves at the beginning of a game of chess;
    chess opening
    
    • he memorized all the important chess openings
13. the first of a series of actions;
    first step, initiative, opening move

adj.

1. first or beginning
   
   • the memorable opening bars of Beethoven's Fifth
   • the play's opening scene