A production with no announced closing date; it plays as long as people keep buying tickets.
Most Broadway musicals and some long-running shows elsewhere play an open run: there is no planned end, and the show continues as long as it is selling well. When sales drop, the producers announce a closing date, usually a few weeks to a few months ahead. On PlayhouseFinder a production with no closing date is labeled "Open run".
Also seen as: open-ended run, open ended run