The Collaborative International Dictionary of English v.0.48:

airship \airship\ n.
   1. 1 a steerable self-propelled light-than-air aircraft.

   Syn: dirigible
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

airship
    n 1: a steerable self-propelled aircraft [syn: airship,
         dirigible]

Moby Thesaurus II by Grady Ward, 1.0:

22 Moby Thesaurus words for "airship":
   Graf Zeppelin, aerostat, ballonet, balloon, basket, blimp, car,
   catwalk, dirigible, dirigible balloon, envelope, gas chamber,
   gasbag, gondola, lighter-than-air craft, mooring harness,
   rigid airship, sandbag, semirigid airship, ship, subcloud car,
   zeppelin