sea rover vs corsair

sea rover and corsair both are nouns.

Word	Noun	Adjective	Verb	Adverb
sea rover	Yes	No	No	No
corsair	Yes	No	No	No

As nouns, corsair is a hyponym of sea rover; that is, corsair is a word with a more specific, narrower meaning than sea rover:

sea rover: someone who robs at sea or plunders the land from the sea without having a commission from any sovereign nation
corsair: a pirate along the Barbary Coast

Other hyponyms of sea rover include Barbary pirate, sea king.

sea rover (noun)	corsair (noun)
someone who robs at sea or plunders the land from the sea without having a commission from any sovereign nation	a swift pirate ship (often operating with official sanction)
	a pirate along the Barbary Coast