tycoon vs big businessman

tycoon and big businessman both are nouns.

Word	Noun	Adjective	Verb	Adverb
tycoon	Yes	No	No	No
big businessman	Yes	No	No	No

As nouns, tycoon and big businessman are synonyms defined as:

Other synonyms of tycoon include baron, business leader, king, magnate, mogul, power, top executive.

tycoon (noun)	big businessman (noun)
a very wealthy or powerful businessman	a very wealthy or powerful businessman