The Collaborative International Dictionary of English v.0.48:

Angiosperm \An"gi*o*sperm\ (-[a^]n"j[i^]*[-o]*sp[~e]rm), n.
   [Angio- + Gr. ?, ?, seed.] (Bot.)
   A plant which has its seeds inclosed in a pericarp.
   Contrasted with gymnosperm.
   [1913 Webster]

   Note: The term is restricted to exogenous plants, and applied
         to one of the two grand divisions of these species, the
         other division including gymnosperms, or those which
         have naked seeds. The oak, apple, beech, etc., are
         angiosperms, while the pines, spruce, hemlock, and the
         allied varieties, are gymnosperms.
         [1913 Webster]

WordNet (r) 3.0 (2006):

angiosperm
    n 1: plants having seeds in a closed ovary [syn: angiosperm,
         flowering plant]