Stopper (noun)

1. A device or plug for closing the opening of a container, such as a bottle, jar, or tube.
2. A person or thing that blocks or impedes.
3. A final defensive player in a sport such as soccer or hockey.

Origin:

Mid-15th century: from the verb stop, in the sense "stop up".

Examples:

1. He opened the bottle of wine and inserted the stopper.
2. The stopper prevented the liquid from spilling out of the bottle.
3. She used a cork stopper to seal the bottle of olive oil.
4. He was the stopper in the defense and prevented many goals from being scored.
5. The stopper in the pipeline was causing the blockage.