opposer vs foeman

opposer and foeman both are nouns.

Word	Noun	Adjective	Verb	Adverb
opposer	Yes	No	No	No
foeman	Yes	No	No	No

As nouns, foeman is a hyponym of opposer; that is, foeman is a word with a more specific, narrower meaning than opposer:

opposer: someone who offers opposition
foeman: an armed adversary (especially a member of an opposing military force)

Other hyponyms of opposer include dueler, duelist, dueller, duellist, enemy, foe, opposition, Luddite, withstander.

opposer (noun)	foeman (noun)
someone who offers opposition	an armed adversary (especially a member of an opposing military force)