stopper

stop·per

1. A device, such as a cork or plug, that is inserted to close an opening.
2. One that causes something to stop: a conversation stopper.
3. Baseball A relief pitcher, especially one called upon to protect a lead.
4. Sports
   a. A player who excels on defense, as in basketball.
   b. In soccer, a defensive player who plays behind the center midfielder and often guards the opponent's best forward.
   c. A goalie.
5. Games A card or cards preventing one's opponents from winning all the tricks in a particular suit in a hand of bridge.