WordNet (r) 3.0 (2006):

sailplane
    n 1: aircraft supported only by the dynamic action of air
         against its surfaces [syn: glider, sailplane]
    v 1: fly a plane without an engine [syn: sailplane, soar]

Moby Thesaurus II by Grady Ward, 1.0:

26 Moby Thesaurus words for "sailplane":
   aeroplane, airlift, airplane, balloon, be airborne, cruise, drift,
   ferry, flit, fly, glide, glider, gliding machine, hop, hover,
   hydroplane, jet, navigate, rocket glider, sail, seaplane, soar,
   take the air, take wing, volplane, wing