idempotentPronunciation: /ˌʌɪdɛmˈpəʊt(ə)nt, ʌɪˈdɛmpət(ə)nt/ MathematicsDefinition of idempotent adjective denoting an element of a set which is unchanged in value when multiplied or otherwise operated on by itself. noun an idempotent element. Origin: late 19th century: from Latin idem 'same' + potent1idempotent in other Oxford dictionaries Definition of idempotent in the US English dictionary