rustler vs thief

rustler and thief both are nouns.

Word	Noun	Adjective	Verb	Adverb
rustler	Yes	No	No	No
thief	Yes	No	No	No

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

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

Other hypernyms of rustler include stealer.

rustler (noun)	thief (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