thighn.[OE. thi, ih, eh, AS. eh; akin to OFries. thiach, D. dij, dije, OHG. dioh, thioh, Icel. j thigh, rump, and probably to Lith. taukas fat of animals, tukti to become fat, Russ. tuke fat of animals. 56.]1. (Anat.) The proximal segment of the hind limb between the knee and the trunk. See Femur.()2. (Zol.) The coxa, or femur, of an insect.()Thigh bone (Anat.), the femur.()