old salt vs Jack-tar

old salt and Jack-tar both are nouns.

Word	Noun	Adjective	Verb	Adverb
old salt	Yes	No	No	No
Jack-tar	Yes	No	No	No

As nouns, old salt and Jack-tar are synonyms defined as:

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

old salt (noun)	Jack-tar (noun)
a man who serves as a sailor	a man who serves as a sailor