pickpocket vs stealer

pickpocket and stealer both are nouns.

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

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

pickpocket: a thief who steals from the pockets or purses of others in public places
stealer: a criminal who takes property belonging to someone else with the intention of keeping it or selling it

Other hypernyms of pickpocket include thief.

pickpocket (noun)	stealer (noun)
a thief who steals from the pockets or purses of others in public places	a criminal who takes property belonging to someone else with the intention of keeping it or selling it