The Collaborative International Dictionary of English v.0.48:

crampbark \crampbark\ n.
   a deciduous thicket-forming Old World shrub (Viburnum
   opulus) with clusters of white flowers and small bright red
   berries.

   Syn: guelder rose, European cranberrybush, European cranberry
        bush, cranberry-tree, Viburnum opulus.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

crampbark
    n 1: deciduous thicket-forming Old World shrub with clusters of
         white flowers and small bright red berries [syn: guelder
         rose, European cranberrybush, European cranberry bush,
         crampbark, cranberry tree, Viburnum opulus]