Adversary - (Webster's 1828 Dictionary)
AD'VERSARY, n. [See Adverse.]
1. An enemy or foe; one who has enmity at heart.
The Lord shall take vengeance on his adversaries. Nahum 1.
In scripture, Satan is called THE adversary, by way of eminence. 1 Pet 5.
2. An opponent or antagonist, as in a suit at law, or in single combat; an opposing litigant.
AD'VERSARY, a. Opposed; opposite to; adverse. In law, having an opposing party, as an adversary suit; in distinction from an application, in law or equity, to which no opposition is made.