Derangement/dɪˈreɪndʒmənt/ Definition 1 of 3Pro Tip 1/3Mental State Describes a serious condition, avoid using lightly as a joke. After the accident, his speech suggested some degree of derangement. Pro Tip 2/3Not Insulting Use with sensitivity, as it relates to mental health. The novel portrayed the character's descent into derangement. Pro Tip 3/3Serious Tone Often conveys a somber, clinical observation, not casual. The psychiatrist diagnosed her with a temporary derangement.