The Collaborative International Dictionary of English v.0.48:

Thimbleberry \Thim"ble*ber`ry\, n. (Bot.)
   A kind of black raspberry (Rubus occidentalis), common in
   America.
   [1913 Webster]

WordNet (r) 3.0 (2006):

thimbleberry
    n 1: shrubby raspberry of eastern North America having showy
         rose to purplish flowers and red or orange thimble-shaped
         fruit [syn: flowering raspberry, purple-flowering
         raspberry, Rubus odoratus, thimbleberry]
    2: white-flowered raspberry of western North America and
       northern Mexico with thimble-shaped orange berries [syn:
       salmonberry, salmon berry, thimbleberry, Rubus
       parviflorus]
    3: raspberry native to eastern North America having black
       thimble-shaped fruit [syn: black raspberry, blackcap,
       blackcap raspberry, thimbleberry, Rubus occidentalis]