WordNet (r) 3.0 (2006):

panpipe
    n 1: a primitive wind instrument consisting of several parallel
         pipes bound together [syn: panpipe, pandean pipe,
         syrinx]

Moby Thesaurus II by Grady Ward, 1.0:

49 Moby Thesaurus words for "panpipe":
   English horn, Pandean pipe, aulos, basset horn, basset oboe,
   bassoon, bombard, clarinet, contrabassoon, contrafagotto, cromorne,
   double bassoon, double reed, fife, fipple flute, flageolet, flute,
   hautboy, heckelphone, hornpipe, licorice stick, musette,
   oaten reed, oboe, oboe da caccia, ocarina, penny-whistle, piccolo,
   pipe, pommer, recorder, reed, reed instrument, sax, saxophone,
   shawm, single reed, single-reed instrument, sonorophone,
   sweet potato, syrinx, tabor pipe, tenoroon, tin-whistle, whistle,
   woods, woodwind, woodwind choir, woodwind instrument