talkative vs blabbermouthed

talkative and blabbermouthed both are adjectives.

Word	Noun	Adjective	Verb	Adverb
talkative	No	Yes	No	No
blabbermouthed	No	Yes	No	No

As adjectives, talkative and blabbermouthed are synonyms defined as:

Other synonyms of talkative include bigmouthed, blabby.

talkative (adjective)	blabbermouthed (adjective)
friendly and open and willing to talk	prone to communicate confidential information
unwisely talking too much	unwisely talking too much
full of trivial conversation