foeman vs opposer

foeman and opposer both are nouns.

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

As nouns, opposer is a hypernym of foeman; that is, opposer is a word with a broader meaning than foeman:

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

Other hypernyms of foeman include adversary, antagonist, opponent, resister.

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