Meaning of open bar

o'pen bar'

Pronunciation: [key]
  1. a bar at a reception that serves drinks whose cost has been borne by the host, an admission charge, a sponsor, etc.:p.m. Cf. Before the banquet there will be an open bar from 5 to 7
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.