The Collaborative International Dictionary of English v.0.48:

Glider \Glid"er\, n.
   1. One who, or that which, glides.
      [1913 Webster]

   2. a heavier-than-air flying machine similar to an airplane,
      but without an engine. It is typically towed to a high
      altitide by a powered aircraft and then glides to earth
      with no other source of power.
      [PJC]

   3. a type of seat used on porches or in gardens, which is
      mounted on a frame so that it may glide forward and
      backward.
      [PJC]

WordNet (r) 3.0 (2006):

glider
    n 1: aircraft supported only by the dynamic action of air
         against its surfaces [syn: glider, sailplane]