The Collaborative International Dictionary of English v.0.48:

Typhoon \Ty*phoon"\, n. [Earlier tuffoon, tuffon, Pg. tuf[~a]o,
   Ar. tuf[=a]n a violent storm; probably fr. Gr. tyfw^n,
   tyfw^s, a violent whirlwind, that rushes upward from the
   earth, whirling clouds of dust (cf. Typhus); or perhaps
   from Chin. t'ai-fung a cyclonic wind.]
   A violent whirlwind; specifically, a violent whirlwind
   occurring in the Chinese seas.
   [1913 Webster]

WordNet (r) 3.0 (2006):

typhoon
    n 1: a tropical cyclone occurring in the western Pacific or
         Indian oceans

Moby Thesaurus II by Grady Ward, 1.0:

51 Moby Thesaurus words for "typhoon":
   baguio, black squall, blizzard, blow, cyclone, dirty weather,
   dust devil, equinoctial, foul weather, gale, half a gale,
   heavy blow, hurricane, ill wind, line squall, line storm,
   rainspout, rainstorm, rotary storm, rough weather, sand column,
   sandspout, snowstorm, squall, squall line, storm, storm wind,
   stormy weather, stormy winds, strong wind, tempest,
   tempestuous rage, tempestuous wind, thick squall, thundersquall,
   thunderstorm, tornado, tropical, tropical cyclone, twister,
   ugly wind, violent blow, waterspout, whirlblast, whirlwind,
   white squall, whole gale, williwaw, wind eddy, wind-shift line,
   windstorm