cattle thief vs stealer

cattle thief and stealer both are nouns.

Word	Noun	Adjective	Verb	Adverb
cattle thief	Yes	No	No	No
stealer	Yes	No	No	No

As nouns, stealer is a hypernym of cattle thief; that is, stealer is a word with a broader meaning than cattle thief:

cattle thief: someone who steals livestock (especially cattle)
stealer: a criminal who takes property belonging to someone else with the intention of keeping it or selling it

Other hypernyms of cattle thief include thief.

cattle thief (noun)	stealer (noun)
someone who steals livestock (especially cattle)	a criminal who takes property belonging to someone else with the intention of keeping it or selling it