big businessman vs top executive

big businessman and top executive both are nouns.

Word	Noun	Adjective	Verb	Adverb
big businessman	Yes	No	No	No
top executive	Yes	No	No	No

As nouns, big businessman and top executive are synonyms defined as:

big businessman and top executive: a very wealthy or powerful businessman

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

big businessman (noun)	top executive (noun)
a very wealthy or powerful businessman	a very wealthy or powerful businessman