(n.) A Latin adverb and preposition, signifying against, contrary, in opposition, etc., entering as a prefix into the composition of many English words. Cf. Counter, adv. & pref.

a rebours adverse to against against the grain against the tide against the wind antipode antipodes antipole antithesis antonym arsy-varsy at cross-purposes at cross-purposes with at daggers at daggers drawn at issue at odds at variance at war with athwart by contraries con contradictory contrarily contrariously contrariwise contrary contrawise converse conversely counter counter to counterbalance countercheck counterpoint counterpoise counterpole counterterm cross dead against eyeball-to-eyeball facing foil fronting in conflict with in confrontation in flat opposition in hostile array in opposition in opposition to inverse inversely just the opposite nay rather obverse offset on the contrary opposed to opposite opposite number oppositely otherwise over per contra quite the contrary rather reverse setoff the contrary the other side to the contrary topsy-turvy tout au contraire toward up in arms upside down versus vice versa vis-a-vis with crossed bayonets