A no-host bar is a bar at a social event where guests are required to pay for their own drinks, according to Reference.com. The opposite of a no-host bar is an open bar, in which the person hosting the party pays for the guests' drinks.
A no-host bar is also called a cash bar because credit cards and checks are often not taken at the temporary bar set-ups within the parties. Guests invited to a no-host bar wedding, anniversary party, bridal shower or other type of social event must have cash on hand to pay for their alcoholic or non-alcoholic drinks. The guests are also responsible for tipping the bartenders and servers for services rendered.