noun

• (drama) A release of emotional tension after an overwhelming vicarious experience, resulting in the purging or purification of the emotions, as through watching a dramatic production (especially a tragedy).
• Any release of emotional tension to the same effect, more widely.
• A purification or cleansing, especially emotional.
• (psychology) A therapeutic technique to relieve tension by re-establishing the association of an emotion with the memory or idea of the event that first caused it, and then eliminating it by complete expression (called the abreaction).
• (medicine) Purging of the digestive system.