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Synonyms for Blab (same or very similar meaning)

WordNet sense 1 (speak (about unimportant matters) rapidly and incessantly):
blabber, chatter, clack, gabble, gibber, maunder, palaver, piffle, prate, prattle, tattle, tittle-tattle, twaddle

WordNet sense 2 (divulge confidential information or secrets):
babble, peach, sing, talk, spill the beans, babble out, blab out, let the cat out of the bag

From the ODE community, based on WordNetadd/edit