n. & adj.
--n.
1. an aperture or gap, esp. allowing access.
2 a favourable situation or opportunity.
3 a beginning; an initial part.
4 Chess a recognized sequence of moves at the beginning of a game.
5 a counsel's preliminary statement of a case in a lawcourt.
--adj. initial, first.
Phrases and idioms:
opening-time Brit. the time at which public houses may legally open for custom.