shit vs defecation

shit and defecation both are nouns.

Word	Noun	Adjective	Verb	Adverb
shit	Yes	No	Yes	No
defecation	Yes	No	No	No

As nouns, defecation is a hypernym of shit; that is, defecation is a word with a broader meaning than shit:

Other hypernyms of shit include laxation, shitting.

shit (noun)	defecation (noun)
something of little value	the elimination of fecal waste through the anus
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

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