gossip vs blabbermouth

gossip and blabbermouth both are nouns.

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

As nouns, blabbermouth is a hyponym of gossip; that is, blabbermouth is a word with a more specific, narrower meaning than gossip:

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

Other hyponyms of gossip include cat, scandalmonger, talebearer, taleteller, tattler, tattletale, telltale, yenta.

gossip (noun)	blabbermouth (noun)
light informal conversation for social occasions	someone who gossips indiscreetly
a report (often malicious) about the behavior of other people
a person given to gossiping and divulging personal information about others

gossip (verb)	blabbermouth (verb)
wag one's tongue; speak about others and reveal secrets or intimacies
talk socially without exchanging too much information