be vs knock about

be and knock about both are verbs.

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

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

be (verb)	knock about (verb)
spend or use time	strike against forcefully
work in a specific place, with a specific subject, or in a specific function	be around; be alive or active
have an existence, be extant
have life, be alive
form or compose
have the quality of being; (copula, used with an adjective or a predicate noun)
occupy a certain position or area; be somewhere
be identical to; be someone or something
be identical or equivalent to
represent, as of a character on stage
be priced at
to remain unmolested, undisturbed, or uninterrupted -- used only in infinitive form