The Collaborative International Dictionary of English v.0.48:

Glide path \Glide path\, n. (Aeronautics)
   the proper path for an airplane approaching a landing strip;
   also called glide slope.
   [PJC]

The Collaborative International Dictionary of English v.0.48:

Glide slope \Glide slope\, n. (Aeronautics)
   1. the proper path for an airplane approaching a landing
      strip; also called glide path.
      [PJC]

   2. The path indicated by a radio beacon as the proper path
      for an airplane to use in approaching a landing strip.
      [PJC]

WordNet (r) 3.0 (2006):

glide slope
    n 1: the final path followed by an aircraft as it is landing
         [syn: approach path, approach, glide path, glide
         slope]