Knap has 5 different meanings across 1 category:
Verb
A sharp blow or slap.
A protuberance; a swelling; a knob.
strike sharply
"rap him on the knuckles"
break a small piece off from
"chip the glass"
"chip a tooth"
To shape a brittle material having conchoidal fracture, usually a mineral (flint, obsidian, chert etc.), by breaking away flakes, often forming a sharp edge or point.