bosun vs Jack-tar

bosun and Jack-tar both are nouns.

Word	Noun	Adjective	Verb	Adverb
bosun	Yes	No	No	No
Jack-tar	Yes	No	No	No

As nouns, Jack-tar is a hypernym of bosun; that is, Jack-tar is a word with a broader meaning than bosun:

bosun: a petty officer on a merchant ship who controls the work of other seamen
Jack-tar: a man who serves as a sailor

Other hypernyms of bosun include gob, Jack, mariner, old salt, sea dog, seafarer, seaman, tar.

bosun (noun)	Jack-tar (noun)
a petty officer on a merchant ship who controls the work of other seamen	a man who serves as a sailor