lighterman vs seaman

lighterman and seaman both are nouns.

Word	Noun	Adjective	Verb	Adverb
lighterman	Yes	No	No	No
seaman	Yes	No	No	No

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

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

lighterman (noun)	seaman (noun)
someone who operates a barge	a man who serves as a sailor