sea dog vs sailor

sea dog and sailor both are nouns.

Word	Noun	Adjective	Verb	Adverb
sea dog	Yes	No	No	No
sailor	Yes	No	No	No

As nouns, sailor is a hypernym of sea dog; that is, sailor is a word with a broader meaning than sea dog:

Other hypernyms of sea dog include crewman.

sea dog (noun)	sailor (noun)
a man who serves as a sailor	a stiff hat made of straw with a flat crown
	any member of a ship's crew
	a serviceman in the navy