cowboy vs cowman

cowboy and cowman both are nouns.

Word	Noun	Adjective	Verb	Adverb
cowboy	Yes	No	No	No
cowman	Yes	No	No	No

As nouns, cowboy and cowman are synonyms defined as:

cowboy and cowman: a male hired hand who tends cattle and performs other duties on horseback

Other synonyms of cowboy include cattleman.

cowboy (noun)	cowman (noun)
someone who is reckless or irresponsible (especially in driving vehicles)	a male hired hand who tends cattle and performs other duties on horseback
a performer who gives exhibitions of riding and roping and bulldogging
a male hired hand who tends cattle and performs other duties on horseback