Source : Webster's Revised Unabridged Dictionary (1913)

Sepoy \Se"poy\, n. [Per. sip[=a]h[=i], fr. sip[=a]h an army. Cf.
   {Spahi}.]
   A native of India employed as a soldier in the service of a
   European power, esp. of Great Britain; an Oriental soldier
   disciplined in the European manner.