Source : Webster's Revised Unabridged Dictionary (1913)

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.

Source : WordNet®

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