Longman Dictionary of Contemporary English
Wiktionary
n. A bar at which drinks are served without charge, usually at a social event.
Wikipedia
Open Bar is a gay-themed reality television series. The six episode series follows Tyler Robuck through the planning, construction and opening of a gay bar called iCandy in West Hollywood, California. It also touches on the issues Robuck faced during his coming out process and trying to find a romantic relationship. Open Bar premiered on Logo on August 22, 2005, one of the first original series aired by the channel.
Open Bar is available for download from the iTunes Store.
Usage examples of "open bar".
From my room I could see through the open bar doors and into the bar.
An open bar for two full hours, no maximum, and half price cost thereafter.
And they have an open bar right there and they just leave the bottles out, and champagne and just the best food.
Ryan had seen to all the arrangements, with a big buffet breakfast set out at nine, followed by lunch at noon, and an open bar with coffee and tea all day.
He'd found a spot on the broad curve of paving that surrounded the big circular swimming pool, away from everyone else, but close enough to the open bar to signal to the waiter.
I kept right on going aft and outside, onto the weather deck, past the open bar and the tables, clear to the swimming pool.