The Collaborative International Dictionary of English v.0.48:

Unciform \Un"ci*form\ ([u^]n"s[i^]*f[^o]rm), a. [L. uncus a hook
   + -form.]
   Having the shape of a hook; being of a curved or hooked form;
   hooklike.
   [1913 Webster]

   Unciform bone (Anat.), a bone of the carpus at the bases of
      the fourth and fifth metacarpals; the hamatum.
      [1913 Webster]

WordNet (r) 3.0 (2006):

unciform bone
    n 1: the wrist bone in line with the 4th and 5th fingers [syn:
         hamate, hamate bone, unciform bone, os hamatum]