ad·ver·sa·tive (ād-vûr'sə-tĭv) adj. Expressing antithesis or opposition: the adversative conjunction but. n. A word that expresses antithesis or opposition.
[Latin adversātīvus, from adversātus, past participle of adversārī, to oppose, from adversus, against; see adverse.] ad·ver'sa·tive·ly adv.