(n.) Insanity; madness; esp. that form which consists in weakness or total loss of thought and reason; mental imbecility; idiocy.

aberration abnormality alienation brain damage brainsickness clouded mind craziness daftness dementedness derangement disorientation distraction folie furor insaneness insanity irrationality loss of mind loss of reason lunacy madness mania mental deficiency mental derangement mental disease mental disorder mental disturbance mental illness mental instability mental sickness mind overthrown mindsickness oddness pixilation possession queerness rabidness reasonlessness senselessness shattered mind sick mind sickness strangeness unbalance unbalanced mind unsaneness unsound mind unsoundness unsoundness of mind witlessness