loser vs gambler

loser and gambler both are nouns.

Word	Noun	Adjective	Verb	Adverb
loser	Yes	No	No	No
gambler	Yes	No	No	No

As nouns, gambler is a hypernym of loser; that is, gambler is a word with a broader meaning than loser:

loser: a gambler who loses a bet
gambler: a person who wagers money on the outcome of games or sporting events

loser (noun)	gambler (noun)
a gambler who loses a bet	a person who wagers money on the outcome of games or sporting events
a contestant who loses the contest	someone who risks loss or injury in the hope of gain or excitement
a person with a record of failing; someone who loses consistently