The Collaborative International Dictionary of English v.0.48:

manual alphabet \manual alphabet\ n.
   An alphabet of signs made by movement of the hands, used by
   the deaf; in it letters are represented by finger positions.
   See Dactylology.

   Syn: finger alphabet.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

manual alphabet
    n 1: an alphabet used by the deaf; letters are represented by
         finger positions [syn: manual alphabet, finger
         alphabet]