big businessman vs mogul

big businessman and mogul both are nouns.

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

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

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

big businessman (noun)	mogul (noun)
a very wealthy or powerful businessman	a very wealthy or powerful businessman
	a bump on a ski slope