grenade thrower vs infantryman

grenade thrower and infantryman both are nouns.

Word	Noun	Adjective	Verb	Adverb
grenade thrower	Yes	No	No	No
infantryman	Yes	No	No	No

As nouns, infantryman is a hypernym of grenade thrower; that is, infantryman is a word with a broader meaning than grenade thrower:

Other hypernyms of grenade thrower include foot soldier, footslogger, marcher.

grenade thrower (noun)	infantryman (noun)
an infantryman equipped with grenades	fights on foot with small arms