privateersman vs ship's officer

privateersman and ship's officer both are nouns.

Word	Noun	Adjective	Verb	Adverb
privateersman	Yes	No	No	No
ship's officer	Yes	No	No	No

As nouns, ship's officer is a hypernym of privateersman; that is, ship's officer is a word with a broader meaning than privateersman:

privateersman: an officer or crew member of a privateer
ship's officer: a person authorized to serve in a position of authority on a vessel

Other hypernyms of privateersman include crew member, crewman, officer.

privateersman (noun)	ship's officer (noun)
an officer or crew member of a privateer	a person authorized to serve in a position of authority on a vessel