The Collaborative International Dictionary of English v.0.48:

Blueberry \Blue"berry\, n. [Cf. Blaeberry.] (Bot.)
   The berry of several species of Vaccinium, an ericaceous
   genus, differing from the American huckleberries in
   containing numerous minute seeds instead of ten nutlets. The
   commonest species are Vaccinium Pennsylvanicum and
   Vaccinium vacillans. Vaccinium corymbosum is the tall
   blueberry.
   [1913 Webster]

WordNet (r) 3.0 (2006):

blueberry
    n 1: any of numerous shrubs of the genus Vaccinium bearing
         blueberries [syn: blueberry, blueberry bush]
    2: sweet edible dark-blue berries of either low-growing or high-
       growing blueberry plants