shoplifter vs stealer

shoplifter and stealer both are nouns.

Word	Noun	Adjective	Verb	Adverb
shoplifter	Yes	No	No	No
stealer	Yes	No	No	No

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

shoplifter: a thief who steals goods that are in a store
stealer: a criminal who takes property belonging to someone else with the intention of keeping it or selling it

Other hypernyms of shoplifter include thief.

shoplifter (noun)	stealer (noun)
a thief who steals goods that are in a store	a criminal who takes property belonging to someone else with the intention of keeping it or selling it