med. jur. A weakness of the mind, caused by the absence or obliteration of natural or acquired ideas; or it is described to be an abnormal deficiency either in those faculties which acquaint us with the qualities and ordinary relations of things, or in those which furnish us with the moral motives that regulate our relations and conduct towards our fellow men. It is frequently attended with excessive activity. of one or more of the animal propensities. 2. Imbecility differs from idiocy in this, that the subjects of the former possess some intellectual capacity, though inferior in degree to that possessed by the great mass of mankind; while those of the latter are utterly destitute of reason. Imbecility differs also from stupidity. The former consists in a defect of the mind, which renders it unable to examine the data presented to it by the senses, and therefrom to deduce the correct judgment; that is, a defect of intensity, or reflective power. The latter is occasioned by a want of intensity, or perceptive power. See INSANITY.