Source : Webster's Revised Unabridged Dictionary (1913)

Tycoon \Ty*coon"\ (t[-i]`k[=oo]n"), n. [Chinese tai-kun great
   prince.]
   The title by which the shogun, or former commander in chief
   of the Japanese army, was known to foreigners.

Source : WordNet®

tycoon
     n : a very wealthy or powerful businessman; "an oil baron" [syn:
          {baron}, {big businessman}, {business leader}, {king}, {magnate},
          {mogul}, {power}, {top executive}]