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.

, 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.