oilman vs wildcatter

oilman and wildcatter both are nouns.

Word	Noun	Adjective	Verb	Adverb
oilman	Yes	No	No	No
wildcatter	Yes	No	No	No

As nouns, wildcatter is a hyponym of oilman; that is, wildcatter is a word with a more specific, narrower meaning than oilman:

oilman: a person who owns or operates oil wells
wildcatter: an oilman who drills exploratory wells in territory not known to be an oil field

oilman (noun)	wildcatter (noun)
a worker who produces or sells petroleum	an oilman who drills exploratory wells in territory not known to be an oil field
a person who owns or operates oil wells