business leader vs big businessman

business leader and big businessman both are nouns.

Word	Noun	Adjective	Verb	Adverb
business leader	Yes	No	No	No
big businessman	Yes	No	No	No

As nouns, business leader and big businessman are synonyms defined as:

business leader and big businessman: a very wealthy or powerful businessman

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

business leader (noun)	big businessman (noun)
a very wealthy or powerful businessman	a very wealthy or powerful businessman