WordNet (r) 3.0 (2006):

test pilot
    n 1: a pilot hired to fly experimental airplanes through
         maneuvers designed to test them

Moby Thesaurus II by Grady Ward, 1.0:

33 Moby Thesaurus words for "test pilot":
   aeronaut, aeroplaner, aeroplanist, air pilot, airplanist, analyst,
   analyzer, assayer, astronaut, aviator, barnstormer, birdman,
   captain, cloud seeder, commercial pilot, copilot, crop-duster,
   essayer, experimenter, flier, instructor, jet jockey,
   licensed pilot, pilot, rainmaker, research worker, researcher,
   stunt flier, stunt man, test driver, tester, tryer-out, wingman