hysteria UK /hɪˈstɪəɹiə/US /hɪˈstɛɹiə/ noun4 •Behavior exhibiting excessive or uncontrollable emotions, in a wide range from joy to panic but usually including anxiety or fear. •A mental disorder characterized by emotional excitability etc. without an organic cause. •(informal) Synonym of conversion disorder. •(no longer used, historical) Any disorder of women with some psychiatric symptoms without other diagnosis, ascribed to uterine influences on the female body, lack of pregnancy, or lack of sex. formshysteriae · hysterias