n

motormouth (Anglophile); bigmouth; rattle-brain (Anglophile); gabster (Anglophile); babbler (Супру); talker (Супру); full of crap (driven); yap; prater; ratchet jaw; windblower (4uzhoj); chatterbox (my seat companion was a chatterbox who never once shut up during the whole trip vogeler)

amér.

blowhard (Anglophile); fat-mouth (Anglophile); windbag (a person who talks at length but says little of value Val_Ships)

amér., inform.

loudmouth

argot.

windy; yapper (Putney Heath); a blabbermouth (Laurenef); trippin' (Elian); big mouth (Mirinare); yenta mouth (Vmosk); hoo (VLZ_58); gobshite (КГА); bull-thrower (bigmouth (noun, loudmouth) joe_barb); flake (A personal favorite slang term for an unreliable person is a flake. A flake says they are going to do something and then they don't follow through. The definition is not limited to promise breaking, however. • "Трепло у нас военачальники, тупое и немощное трепло."