bos'n vs old salt

bos'n and old salt both are nouns.

Word	Noun	Adjective	Verb	Adverb
bos'n	Yes	No	No	No
old salt	Yes	No	No	No

As nouns, old salt is a hypernym of bos'n; that is, old salt is a word with a broader meaning than bos'n:

bos'n: a petty officer on a merchant ship who controls the work of other seamen
old salt: a man who serves as a sailor

Other hypernyms of bos'n include gob, Jack-tar, Jack, mariner, sea dog, seafarer, seaman, tar.

bos'n (noun)	old salt (noun)
a petty officer on a merchant ship who controls the work of other seamen	a man who serves as a sailor