adversarial (adj.) Look up adversarial at Dictionary.com
"involving adversaries," by 1892, from adversary (n.) + -al (1). The older adjective was simply adversary (late 14c.), but the tendency to confuse it with the noun of the same form probably led to the creation of fresh adjectives (earlier examples are adversative, 1530s; adversarious, 1826). Related: Adversarially.