The Collaborative International Dictionary of English v.0.48:

Cranberry \Cran"ber*ry\ (kr[a^]n"b[e^]r*r[y^]), n.; pl.
   Cranberries (-r[i^]z). [So named from its fruit being ripe
   in the spring when the cranes return. --Dr. Prior.] (Bot.)
   A red, acid berry, much used for making sauce, etc.; also,
   the plant producing it (several species of Vaccinum or
   Oxycoccus.) The high cranberry or cranberry tree is a
   species of Viburnum (Viburnum Opulus), and the other is
   sometimes called low cranberry or marsh cranberry to
   distinguish it.
   [1913 Webster] cranberry tree

The Collaborative International Dictionary of English v.0.48:

cranberry tree \cranberry tree\, cranberry-tree
\cranberry-tree\n.
   a deciduous thicket-forming Old World shrub (Viburnum
   opulus) with clusters of white flowers and small bright red
   berries. It is sometimes called high cranberry to
   distinguish it from the marsh cranberry or low cranberry.

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