The Collaborative International Dictionary of English v.0.48:

Laocoon \La*oc"o*["o]n\, prop. n. [L., fr. Gr. ? ]
   1. (Class. Myth.) A priest of Apollo, during the Trojan war.
      (See 2.)
      [1913 Webster]

   2. (Sculp.) A marble group in the Vatican at Rome,
      representing the priest Laoco["o]n, with his sons,
      infolded in the coils of two serpents, as described by
      Virgil.
      [1913 Webster]

WordNet (r) 3.0 (2006):

Laocoon
    n 1: (Greek mythology) the priest of Apollo who warned the
         Trojans to beware of Greeks bearing gifts when they wanted
         to accept the Trojan Horse; a god who favored the Greeks
         (Poseidon or Athena) sent snakes who coiled around Laocoon
         and his two twin sons killing them

The Devil's Dictionary (1881-1906):

LAOCOON, n.  A famous piece of antique scripture representing a priest
of that name and his two sons in the folds of two enormous serpents.
The skill and diligence with which the old man and lads support the
serpents and keep them up to their work have been justly regarded as
one of the noblest artistic illustrations of the mastery of human
intelligence over brute inertia.