The Collaborative International Dictionary of English v.0.48:

Ankle \An"kle\ ([a^][ng]"k'l), n. [OE. ancle, anclow, AS.
   ancleow; akin to Icel. ["o]kkla, ["o]kli, Dan. and Sw. ankel,
   D. enklaauw, enkel, G. enkel, and perh. OHG. encha, ancha
   thigh, shin: cf. Skr. anga limb, anguri finger. Cf.
   Haunch.]
   The joint which connects the foot with the leg; the tarsus.
   [1913 Webster]

   Ankle bone, the bone of the ankle; the astragalus.
      [1913 Webster]

WordNet (r) 3.0 (2006):

ankle
    n 1: a gliding joint between the distal ends of the tibia and
         fibula and the proximal end of the talus [syn: ankle,
         ankle joint, mortise joint, articulatio talocruralis]

Moby Thesaurus II by Grady Ward, 1.0:

67 Moby Thesaurus words for "ankle":
   articulation, bayonet legs, boundary, bowlegs, butt, calf, cervix,
   clinch, closure, cnemis, connecting link, connecting rod,
   connection, coupling, dovetail, drumstick, elbow, embrace, foreleg,
   gamb, gambrel, gigot, gliding joint, ham, hind leg, hinge,
   hinged joint, hip, hock, interface, jamb, join, joining, joint,
   juncture, knee, knuckle, leg, limb, link, miter, mortise, neck,
   pivot, pivot joint, podite, popliteal space, rabbet, scarf,
   scissor-legs, seam, shank, shin, shoulder, stems, stitch, stumps,
   suture, symphysis, tarsus, tie rod, toggle, toggle joint, trotters,
   union, weld, wrist