1. Loud, shaking or convulsive laughter: Ivan's cachinnations at public gatherings tend to make people stay away when they know that he will be there, too.
2. In medicine, excessive, inappropriate, loud laughter without any apparent reason: There are those who have periods of hysterical laughter, known as cachinnation, as a result of schizophrenia, a mental disorder that alters normal perception, language, and communication.