WordNet (r) 3.0 (2006):

launching pad
    n 1: a platform from which rockets or space craft are launched
         [syn: launching pad, launchpad, launch pad, launch
         area, pad]

Moby Thesaurus II by Grady Ward, 1.0:

33 Moby Thesaurus words for "launching pad":
   Mark, balcony, bazooka, calliope, catafalque, dais, emplacement,
   estrade, floor, gallery, hedgehog, heliport, hustings, landing,
   landing pad, landing stage, launch pad, launching platform,
   launching tube, mousetrap, platform, podium, projector, pulpit,
   rostrum, silo, soapbox, stage, step terrace, stump, terrace,
   tribunal, tribune