The Collaborative International Dictionary of English v.0.48:

Whortleberry \Whor"tle*ber`ry\, n. [AS. wyrtil a small shrub
   (dim. of wyrt wort) + E. berry. See Wort, and cf.
   Huckleberry, Hurtleberry.] (Bot.)
   (a) In England, the fruit of Vaccinium Myrtillus; also, the
       plant itself. See Bilberry, 1.
   (b) The fruit of several shrubby plants of the genus
       Gaylussacia; also, any one of these plants. See
       Huckleberry.
       [1913 Webster]

WordNet (r) 3.0 (2006):

whortleberry
    n 1: erect European blueberry having solitary flowers and blue-
         black berries [syn: bilberry, whortleberry,
         whinberry, blaeberry, Viccinium myrtillus]
    2: blue-black berries similar to American blueberries [syn:
       bilberry, whortleberry, European blueberry]