loudmouth

from WordNet (r) 3.0 (2006)

loudmouth
    n 1: a person who causes trouble by speaking indiscreetly [syn:
         {loudmouth}, {blusterer}]

from The Collaborative International Dictionary of English v.0.48

loud-mouth \loud-mouth\ n.
   1. a person who causes trouble by speaking indiscretely.
      [WordNet sense 1]

   Syn: loudmouth, blusterer.
        [WordNet 1.5]

   2. Aperson who is loud-mouthed.
      [PJC]