The Collaborative International Dictionary of English v.0.48:

Oregon grape \Or"e*gon grape`\ ([o^]r"[-e]*g[o^]n gr[=a]p`).
   (Bot.)
   An evergreen species of barberry (Berberis Aquifolium), of
   Oregon and California; also, its roundish, blue-black
   berries.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Oregon grape
    n 1: small shrub with grey-green leaves and yellow flowers
         followed by glaucous blue berries [syn: Oregon grape,
         Mahonia nervosa]
    2: ornamental evergreen shrub of Pacific coast of North America
       having dark green pinnate leaves and racemes of yellow
       flowers followed by blue-black berries [syn: Oregon grape,
       Oregon holly grape, hollygrape, mountain grape, holly-
       leaves barberry, Mahonia aquifolium]