The Collaborative International Dictionary of English v.0.48:

Tuille \Tuille\ (tw[i^]l), n. [Cf. F. tuile a tile.]
   In plate armor, a suspended plate in from of the thigh. See
   Illust. of Tasses.
   [1913 Webster]

WordNet (r) 3.0 (2006):

tuille
    n 1: armor plate that protects the hip and thigh