(n.) A prefix meaning against, opposite or opposed to, contrary, or in place of; -- used in composition in many English words. It is often shortened to ant-; as, antacid, antarctic.

adversary adversative adverse adversive alien antagonistic antipathetic antithetic antonymous at cross-purposes balancing clashing compensating competitive con conflicting confronting contradictory contradistinct contrapositive contrarious contrary contrasted converse counter counterbalancing counterpoised countervailing cross dead against disaccordant discordant discrepant dissentient enemy eyeball to eyeball fractious hostile inconsistent inimical inverse negative noncooperative obstinate obverse opponent opposed opposing opposite oppositional oppositive oppugnant overthwart perverse recalcitrant refractory repugnant reverse rival squared off uncooperative unfavorable unfriendly unpropitious