GNU Collaborative International Dictionary of English

Found one definition

1.       
   Instep (?), n. [Formerly also instop, instup.]
   
   [1913 Webster]
   
   
   1. The arched middle portion of the human foot next in front of the ankle joint.
   
   [1913 Webster]
   
   
   2. The part of a shoe, boot, or stocking covering the instep1.
   
   [PJC]
   
   
   3. That part of the hind leg of the horse and allied animals, between the hock, or ham, and the pastern joint.
   
   [1913 Webster]