Source : Webster's Revised Unabridged Dictionary (1913)

Herbivorous \Her*biv"o*rous\, a. (Zo["o]l.)
   Eating plants; of or pertaining to the Herbivora.

Source : WordNet®

herbivorous
     adj : feeding only on plants [ant: {omnivorous}, {insectivorous},
           {carnivorous}]