The Collaborative International Dictionary of English v.0.48:

Thigh \Thigh\ (th[imac]), n. [OE. thi, [thorn]ih, [thorn]eh, AS.
   [thorn]e['o]h; akin to OFries. thiach, D. dij, dije, OHG.
   dioh, thioh, Icel. [thorn]j[=o] thigh, rump, and probably to
   Lith. taukas fat of animals, tukti to become fat, Russ. tuke
   fat of animals. [root]56.]
   1. (Anat.) The proximal segment of the hind limb between the
      knee and the trunk. See Femur.
      [1913 Webster]

   2. (Zool.) The coxa, or femur, of an insect.
      [1913 Webster]

   Thigh bone (Anat.), the femur.
      [1913 Webster]

WordNet (r) 3.0 (2006):

thigh
    n 1: the part of the leg between the hip and the knee
    2: the upper joint of the leg of a fowl [syn: second joint,
       thigh]

Moby Thesaurus II by Grady Ward, 1.0:

36 Moby Thesaurus words for "thigh":
   ankle, bayonet legs, bowlegs, breast, calf, chicken foot, cnemis,
   dark meat, drumstick, foreleg, gamb, gambrel, giblets, gigot, ham,
   hind leg, hock, jamb, knee, leg, limb, neck, oyster, podite,
   popliteal space, scissor-legs, shank, shin, stems, stumps, tarsus,
   trotters, turkey foot, white meat, wing, wishbone