rap vs knock

rap and knock both are nouns.

Word	Noun	Adjective	Verb	Adverb
rap	Yes	No	Yes	No
knock	Yes	No	Yes	No

As nouns, rap and knock are synonyms defined as:

Other synonyms of rap include belt, whack, whang.

As verbs, knock is a hyponym of rap; that is, knock is a word with a more specific, narrower meaning than rap:

As verbs, rap and knock are synonyms defined as:

Other synonyms of rap include pink, tap.

rap (noun)	knock (noun)
the act of hitting vigorously	the act of hitting vigorously
a reproach for some lapse or misdeed	negative criticism
voluble conversation	a vigorous blow
genre of African-American music of the 1980s and 1990s in which rhyming lyrics are chanted to a musical accompaniment; several forms of rap have emerged	the sound of knocking (as on a door or in an engine or bearing)
the sound made by a gentle blow	a bad experience
a gentle blow

rap (verb)	knock (verb)
talk volubly	find fault with; express criticism of; point out real or perceived flaws
strike sharply	knock against with force or violence
perform rap music	rap with the knuckles
make light, repeated taps on a surface	deliver a sharp blow or push
	make light, repeated taps on a surface
	sound like a car engine that is firing too early