take a crap vs shit

take a crap is not a noun while shit is a noun.

Word	Noun	Adjective	Verb	Adverb
take a crap	No	No	Yes	No
shit	Yes	No	Yes	No

As verbs, take a crap and shit are synonyms defined as:

Other synonyms of take a crap include ca-ca, crap, defecate, make, stool, take a shit.

take a crap (noun)	shit (noun)
	something of little value
	Obscene word for unacceptable behavior
	insulting terms of address for people who are stupid or irritating or ridiculous
	a coarse term for defecation
	a small worthless amount
	obscene terms for feces

take a crap (verb)	shit (verb)
have a bowel movement	have a bowel movement
	give away information about somebody