A conventional bid (often the cheapest bid) that conveys little or no information, but mainly marks time while partner describes his hand. For example, with the Multi 2♦ convention, a 2♥ response to 2♦ conveys the information that responder wishes to play in 2♥ if the opener has a weak two bid in hearts, and paves the way for the 2♦ bidder to clarify his hand type.
