Source : Webster's Revised Unabridged Dictionary (1913)

Howler \Howl"er\, n.
   1. One who howls.

   2. (Zo["o]l.) Any South American monkey of the genus
      {Mycetes}. Many species are known. They are arboreal in
      their habits, and are noted for the loud, discordant
      howling in which they indulge at night.

Source : WordNet®

howler
     n 1: a joke that seems extremely funny [syn: {belly laugh}, {sidesplitter},
           {thigh-slapper}, {scream}, {wow}, {riot}]
     2: monkey of tropical South American forests having a loud
        howling cry [syn: {howler monkey}]
     3: a glaring blunder