The Collaborative International Dictionary of English v.0.48:

Omnivorous \Om*niv"o*rous\, a. [L. omnivorus; omnis all + vorate
   to eat greedily. See Voracious.]
   1. All-devouring; eating everything indiscriminately; as,
      omnivorous vanity; an omnivorous intellect.
      [1913 Webster +PJC]

   2. Specifically: (Zool.), Eating both animal and vegetable
      food.
      [1913 Webster] -- Om*niv"o*rous*ness, n.
      [1913 Webster]

WordNet (r) 3.0 (2006):

omnivorous
    adj 1: feeding on both plants and animals [ant: carnivorous,
           herbivorous, insectivorous]

Moby Thesaurus II by Grady Ward, 1.0:

93 Moby Thesaurus words for "omnivorous":
   Apician, a hog for, acquisitive, all-devouring, avaricious, avid,
   bolting, bottomless, cannibal, cannibalistic, carnivorous,
   commensal, coveting, covetous, cramming, crapulent, crapulous,
   devouring, dietetic, dining, eating, edacious, esurient, feeding,
   flesh-eating, fruitarian, gastronomic, glutting, gluttonizing,
   gluttonous, gobbling, gorging, grabby, grain-eating, graminivorous,
   granivorous, grasping, grass-eating, greedy, gulping, guttling,
   guzzling, herbivorous, hoggish, hyperphagic, insatiable, insatiate,
   insect-eating, insectivorous, intemperate, lactovegetarian,
   limitless, man-eating, meat-eating, mensal, mercenary, miserly,
   money-hungry, money-mad, nourishing, nutritious, omophagous,
   overgreedy, pantophagous, phytivorous, phytophagous, piggish,
   plant-eating, polyphagic, postprandial, prandial, predacious,
   preprandial, quenchless, rapacious, ravening, ravenous, slakeless,
   sordid, stuffing, swinish, unappeasable, unappeased, unquenchable,
   unsated, unsatisfied, unslakeable, unslaked, vegetable-eating,
   vegetarian, venal, voracious, wolfing