Noah Webster's New International Dictionary of the English Language

1. (n.) One who opposes; an adversary; an antagonist; a foe.

2. (a.) Situated in front; opposite; hence, opposing; adverse; antagonistic.

3. (n.) One who opposes in a disputation, argument, or other verbal controversy; specifically, one who attacks some theirs or proposition, in distinction from the respondent, or defendant, who maintains it.