n. (pl. oaths) 1 a solemn declaration or undertaking (often naming God) as to the truth of something or as a commitment to future action. 2 a statement or promise contained in an oath (oath of allegiance). 3 a profane or blasphemous utterance; a curse. on (or under) oath having sworn a solemn oath. take (or swear) an oath make such a declaration or undertaking.
[ OE ath f. Gmc ]