A stopper is plug or a cork — it's designed to block the opening of a container by fitting partially inside it. The rubber plug you use to keep your bath water from going down the drain is a type of stopper.
The cork in the neck of a wine bottle is a stopper . Other kinds of stoppers halt or prevent something. A crime stopper keeps criminals at bay, and a conversation stopper is something you say that is so awkward or profound that no one can think of anything to say in response.
Definitions of stopper
noun
blockage consisting of an object designed to fill a hole tightly