Definitions:

1. a recognized sequence of moves at the beginning of a game of chess noun
   • They memorized all the important chess openings.
2. a vacant or unobstructed space that is man-made noun
   • they left a small opening for the cat at the bottom of the door
3. an open or empty space in or between things noun
   • there was a small opening between the trees
4. becoming open or being made open noun
   • The opening of the 1904 World's Fair Exposition was a sight to behold.
5. first or beginning adjective
   • the memorable opening bars of Beethoven's Fifth
6. opportunity especially for employment or promotion noun
   • there is an opening in the sales department
7. the act of opening something noun
   • The ray of light revealed their cautious opening of the door.
8. the first performance, as of a theatrical production noun
   • The opening received rave reviews.
9. the initial part of the introduction noun
   • the opening established the basic theme

Synonyms:

• chess opening
• curtain raising
• first step
• gap
• hatchway
• opening night
• orifice
• porta
• possibility
• possible action
• scuttle