Source : Webster's Revised Unabridged Dictionary (1913)

Oleaceous \O`le*a"ceous\, a. [L. ol['e]aceus of the olive tree.]
   (Bot.)
   Of, pertaining to, or resembling, a natural order of plants
   ({Oleace[ae]}), mostly trees and shrubs, of which the olive
   is the type. It includes also the ash, the lilac, the true
   jasmine, and fringe tree.

Source : WordNet®

oleaceous
     adj : of or pertaining to or characteristic of trees or shrubs of
           the olive family