C1unable to control your feelings or behaviour because you are extremely frightened, angry, excited, etc.: Calm down, you're getting hysterical.The police were accused of hysterical over-reaction.hysterical laughter (= uncontrolled laughter)Becoming too excited and easily upsetMental and psychiatric disorders›informalextremely funny: His last film was hysterical.Humour and humoroushysterically
/-i/adverb›She started laughing/crying hysterically (= without control).Becoming too excited and easily upsetMental and psychiatric disorders