cash bar

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A bar, such as one at a large party, where drinks are sold by the glass.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun US A bar at a social event for which guests are required to pay for the drinks themselves. It is opposed to an open bar, where drinks are paid for by the host.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a counter at a large party where you can purchase drinks by the glass