blabbermouth vs gossiper

blabbermouth and gossiper both are nouns.

Word	Noun	Adjective	Verb	Adverb
blabbermouth	Yes	No	No	No
gossiper	Yes	No	No	No

As nouns, gossiper is a hypernym of blabbermouth; that is, gossiper is a word with a broader meaning than blabbermouth:

blabbermouth: someone who gossips indiscreetly
gossiper: a person given to gossiping and divulging personal information about others

Other hypernyms of blabbermouth include gossip, gossipmonger, newsmonger, rumormonger, rumourmonger.

blabbermouth (noun)	gossiper (noun)
someone who gossips indiscreetly	a person given to gossiping and divulging personal information about others