Source : Webster's Revised Unabridged Dictionary (1913)

Terpene \Ter"pene\, n. [See {Turpentine}.] (Chem.)
   Any one of a series of isomeric hydrocarbons of pleasant
   aromatic odor, occurring especially in coniferous plants and
   represented by oil of turpentine, but including also certain
   hydrocarbons found in some essential oils.

Source : WordNet®

terpene
     n : an unsaturated hydrocarbon obtained from plants