Source : Webster's Revised Unabridged Dictionary (1913)

Crus \Crus\ (kr?s), n.; pl. {Crura} (kr?"r?). [L., the leg.]
   (Anat.)
   (a) That part of the hind limb between the femur, or thigh,
       and the ankle, or tarsus; the shank.
   (b) Often applied, especially in the plural, to parts which
       are supposed to resemble a pair of legs; as, the crura of
       the diaphragm, a pair of muscles attached to it; crura
       cerebri, two bundles of nerve fibers in the base of the
       brain, connecting the medulla and the forebrain.

Source : WordNet®

crus
     n : the leg from the knee to foot
     [also: {crura} (pl)]