Source : Webster's Revised Unabridged Dictionary (1913)

Uncus \Un"cus\, n.; pl. {Unci}. [L.] (Zo["o]l.)
   A hook or claw.

Source : WordNet®

uncus
     n : (biology) any hook-shaped process or part
     [also: {unci} (pl)]

unci
     See {uncus}