extreme adj (extremer, extremest) 1 very high, or highest, in degree or intensity. 2 very far, or furthest, in any direction, especially out from the centre. 3 very violent or strong. 4 not moderate; severe • extreme measures. noun 1 either of two people or things as far, or as different, as possible from each other. 2 the highest limit; the greatest degree of any state or condition. extremely adverb to an extreme degree. go to extremes to take action beyond what is thought to be reasonable. in the extreme to the highest degree. ETYMOLOGY: 15c: from Latin extremus, from exterus on the outside.