[1] : The Collaborative International Dictionary of English v.0.48

rhododendron \rho`doden"dron\, n. l., fr. gr. "rodo`dendron,
   literally, rose tree; "ro`don rose + de`ndron tree. see
   rose. bot.
   a genus of shrubs or small trees, often having handsome
   evergreen leaves, and remarkable for the beauty of their
   flowers; rosebay.
   1913 webster
see also:
rose 

[2] : WordNet (r) 2.0

rhododendron
     n : any shrub of the genus rhododendron: evergreen shrubs or
         small shrubby trees having leathery leaves and showy
         clusters of campanulate bell-shaped flowers

Rhododendron >> R Words
Rhododendron, definition of term: Rhododendron
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