1
vb blab, burble, cackle, chatter, gabble, gibber, gurgle, jabber, mumble, murmur, mutter, prate, prattle, rabbit (on) (Brit. informal) run off at the mouth (slang) waffle (informal, chiefly Brit.)
2
n burble, clamour, drivel, gabble, gibberish, murmur, waffle (informal, chiefly Brit.)