knock about vs buffet

knock about is not a noun while buffet is a noun.

Word	Noun	Adjective	Verb	Adverb
knock about	No	No	Yes	No
buffet	Yes	No	Yes	No

As verbs, knock about and buffet are synonyms defined as:

Other synonyms of knock about include batter.

knock about (noun)	buffet (noun)
	a piece of furniture that stands at the side of a dining room; has shelves and drawers
	usually inexpensive bar
	a meal set out on a buffet at which guests help themselves

knock about (verb)	buffet (verb)
strike against forcefully	strike against forcefully
be around; be alive or active	strike, beat repeatedly