lighterman vs Jack-tar

lighterman and Jack-tar both are nouns.

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

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

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

lighterman (noun)	Jack-tar (noun)
someone who operates a barge	a man who serves as a sailor