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):

Vaccinium pennsylvanicum
    n 1: low-growing deciduous shrub of northeastern North America
         having flowers in compact racemes and bearing sweet dark
         blue berries [syn: low-bush blueberry, low blueberry,
         Vaccinium angustifolium, Vaccinium pennsylvanicum]