The Collaborative International Dictionary of English v.0.48:

Haunch \Haunch\ (h[aum]nch; 277), n. [F. hanche, of German
   origin; cf. OD. hancke, hencke, and also OHG. ancha; prob.
   not akin to E. ankle.]
   1. The hip; the projecting region of the lateral parts of the
      pelvis and the hip joint; the hind part.
      [1913 Webster]

   2. Of meats: The leg and loin taken together; as, a haunch of
      venison.
      [1913 Webster]

   Haunch bone. See Innominate bone, under Innominate.

   Haunches of an arch (Arch.), the parts on each side of the
      crown of an arch. (See Crown, n., 11.) Each haunch may
      be considered as from one half to two thirds of the half
      arch.
      [1913 Webster]