Nouns

(n)show-stopper, showstopper, stopperan act so striking or impressive that the show must be delayed until the audience quiets down
(n)conversation stopper, stoppera remark to which there is no polite conversational reply
(n)stopper(bridge) a playing card with a value sufficiently high to insure taking a trick in a particular suit“if my partner has a spade stopper I can bid no trump”
(n)plug, stopper, stoppleblockage consisting of an object designed to fill a hole tightly

Verbs

(v)stopper, stoppleclose or secure with or as if with a stopper“She stoppered the wine bottle”, “The mothers stoppered their babies' mouths with pacifiers”