mouthful /ˈmaʊθfʊl/noun 4adjective 1forms 4phrases 1 noun4 •The amount that will fit in a mouth.He swallowed a mouthful of sea water when he fell in. •Something difficult to pronounce or say.“She sells sea shells” is a bit of a mouthful to say. •A tirade of abusive language. •(slang) Quite a bit. adjective1 •Bombastic or awkward.Once this happens to be the result, there is little reason for waxing over such mouthful phrases as 'grass-roots democracy', 'democratic decentralization' or 'panchayati raj'. — 1977 formsmouthfuls · mouthsful · more mouthful · most mouthful Phrases with mouthful mouthful of marblesAn indistinct, muffled or garbled manner of speaking.