The Collaborative International Dictionary of English v.0.48:

Adiantum \Ad`i*an"tum\, n. [L., fr. Gr. 'adi`anton, maidenhair;
   'a priv. + diai`nein to wet.] (Bot.)
   A genus of ferns, the leaves of which shed water; maidenhair.
   Also, the black maidenhair, a species of spleenwort.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Adiantum
    n 1: cosmopolitan genus of ferns: maidenhair ferns; in some
         classification systems placed in family Polypodiaceae or
         Adiantaceae [syn: Adiantum, genus Adiantum]