The Collaborative International Dictionary of English v.0.48:

Leading edge \Lead"ing edge\n.
   1. (Aeronautics) the front edge of an airfoil; same as
      Advancing edge, above.
      [Webster 1913 Suppl.]

   2. the front edge of anything that moves; also used
      metaphorically, as the leading edge in art. See also
      cutting edge.
      [PJC]

The Collaborative International Dictionary of English v.0.48:

Advancing edge \Ad*van"cing edge\ (A["e]ronautics)
   The front edge (in direction of motion) of a supporting
   surface; -- contr. with following edge, which is the rear
   edge.
   [Webster 1913 Suppl.]