leatherneck vs shipboard soldier

leatherneck and shipboard soldier both are nouns.

Word	Noun	Adjective	Verb	Adverb
leatherneck	Yes	No	No	No
shipboard soldier	Yes	No	No	No

As nouns, leatherneck and shipboard soldier are synonyms defined as:

leatherneck and shipboard soldier: a member of the United States Marine Corps

Other synonyms of leatherneck include devil dog, Marine.

leatherneck (noun)	shipboard soldier (noun)
a member of the United States Marine Corps	a member of the United States Marine Corps