The Collaborative International Dictionary of English v.0.48:

Deciduous \De*cid"u*ous\ (?; 135), a. [L. deciduus, fr. dec?dere
   to fall off; de- + cadere to fall. See Chance.] (Biol.)
   Falling off, or subject to fall or be shed, at a certain
   season, or a certain stage or interval of growth, as leaves
   (except of evergreens) in autumn, or as parts of animals,
   such as hair, teeth, antlers, etc.; also, shedding leaves or
   parts at certain seasons, stages, or intervals; as, deciduous
   trees; the deciduous membrane.
   [1913 Webster]

WordNet (r) 3.0 (2006):

deciduous
    adj 1: (of plants and shrubs) shedding foliage at the end of the
           growing season [ant: evergreen]
    2: (of teeth, antlers, etc.) being shed at the end of a period
       of growth; "deciduous teeth"