The Collaborative International Dictionary of English v.0.48:

Oleaster \O`le*as"ter\, n. [L., fr. olea olive tree. See
   Olive, Oil.] (Bot.)
   (a) The wild olive tree (Olea Europea, var. sylvestris).
   (b) Any species of the genus Elaeagus. See Eleagnus. The
       small silvery berries of the common species (Elaeagnus
       hortensis) are called Trebizond dates, and are made
       into cakes by the Arabs.
       [1913 Webster]

WordNet (r) 3.0 (2006):

oleaster
    n 1: any of several shrubs of the genus Elaeagnus having silver-
         white twigs and yellow flowers followed by olivelike fruits