The Collaborative International Dictionary of English v.0.48:
Whitebeam \White"beam`\, n. (Bot.) The common beam tree of England (Pyrus Aria); -- so called from the white, woolly under surface of the leaves. [1913 Webster]The Collaborative International Dictionary of English v.0.48:
Beam tree \Beam" tree`\ [AS. be['a]m a tree. See Beam.] (Bot.) A tree (Pyrus aria) related to the apple. [1913 Webster]