The Collaborative International Dictionary of English v.0.48:

Laughingstock \Laugh"ing*stock`\, n.
   An object of ridicule; a butt of sport. --Shak.
   [1913 Webster]

         When he talked, he talked nonsense, and made himself
         the laughingstock of his hearers.        --Macaulay.
   [1913 Webster]

WordNet (r) 3.0 (2006):

laughingstock
    n 1: a victim of ridicule or pranks [syn: butt, goat,
         laughingstock, stooge]

Moby Thesaurus II by Grady Ward, 1.0:

20 Moby Thesaurus words for "laughingstock":
   butt, byword, byword of reproach, derision, dupe, fair game,
   figure of fun, fool, game, gazingstock, goat, jest, jestingstock,
   joke, mockery, monkey, stock, target, toy, victim