Noun

1. A close-fitting head covering either without a brim or with a peak.
2. A special head covering to indicate rank, occupation etc.
3. An academic mortarboard
4. A protective cover or seal
5. A crown for covering a tooth
6. The summit of a mountain etc.
7. An artificial upper limit or ceiling
8. The top part of a mushroom
9. The cap worn by players as protection from the sun; the cap awarded to a player when first selected to play for a side
10. A small amount of gunpowder in a paper strip or plastic cup for use in a toy gun

    Billy spent all morning firing caps with his friends, re-enacting storming the beach at Normandy.

11. A small explosive device used to detonate a larger charge of explosives

    He wired the cap to the bundle of dynamite, then detonated it remotely.

12. A bullet used to shoot someone.
    • 2001: Charles Jade, Jade goes to Metreon

      Did he think they were going to put a cap in his ass right in the middle of Metreon?

13. An international appearance

    Rio Ferdinand won his 50th cap for England in a game against Sweden.

Verb

1. To cover or seal with a cap
2. To award a cap as a mark of distinction etc.
3. To lie over or on top of something
4. To surpass or outdo
5. To set an upper limit on something
6. To select a player to play for a specified side
7. To shoot someone

   If he don't get outta my hood, I'm gonna cap his ass.

Verb

1. To convert text to uppercase

Etymology 3