From The Collaborative International Dictionary of English v.0.48 [gcide]:
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.
[1913 Webster]
From WordNet (r) 3.0 (2006) [wn]:
tycoon
n 1: a very wealthy or powerful businessman; "an oil baron"
[syn: baron, big businessman, business leader,
king, magnate, mogul, power, top executive,
tycoon]