seafarer vs Jack

seafarer and Jack both are nouns.

Word	Noun	Adjective	Verb	Adverb
seafarer	Yes	No	No	No
Jack	Yes	No	No	No

As nouns, seafarer and Jack are synonyms defined as:

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

seafarer (noun)	Jack (noun)
a man who serves as a sailor	a man who serves as a sailor