cap
noun
1.
a tight-fitting headdress
2.
a top (as for a bottle)
3.
a mechanical or electrical explosive device or a small amount of explosive; can be used to initiate the reaction of a disrupting explosive
4.
something serving as a cover or protection
5.
a fruiting structure resembling an umbrella or a cone that forms the top of a stalked fleshy fungus such as a mushroom
6.
a protective covering that is part of a plant
8.
(dentistry) dental appliance consisting of an artificial crown for a broken or decayed tooth