Source : Webster's Revised Unabridged Dictionary (1913)

Roarer \Roar"er\, n.
   1. One who, or that which, roars. Specifically:
      (a) A riotous fellow; a roaring boy.

                A lady to turn roarer, and break glasses.
                                                  --Massinger.
      (b) (Far.) A horse subject to roaring. See {Roaring}, 2.

   2. (Zo["o]l.) The barn owl. [Prov. Eng.]

Source : WordNet®

roarer
     n : someone who communicates vocally in a very loud voice [syn:
         {bawler}, {bellower}, {screamer}, {screecher}, {shouter},
          {yeller}]