steersman vs Jack

steersman and Jack both are nouns.

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

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

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

steersman (noun)	Jack (noun)
the person who steers a ship	a man who serves as a sailor