inverted talon

from The Collaborative International Dictionary of English v.0.48
Talon \Tal"on\, n. [F., heel, spur, LL. talo, fr. L. talus the
   ankle, heel.]
   1. The claw of a predaceous bird or animal, especially the
      claw of a bird of prey. --Bacon.
      [1913 Webster]

   2. (Zool.) One of certain small prominences on the hind part
      of the face of an elephant's tooth.
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   3. (Arch.) A kind of molding, concave at the bottom and
      convex at the top; -- usually called an {ogee}.
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   Note: When the concave part is at the top, it is called an
         {inverted talon}.
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   4. The shoulder of the bolt of a lock on which the key acts
      to shoot the bolt. --Knight.
      [1913 Webster] Talook
    

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