Definition: Rain4 is a Greek term that translates to "thunderstorm" in English, referring specifically to heavy rain falling over an area quickly followed by thunderous sound. The term comes from ancient Greece where people often referred to sudden rains as a thundering or clashing force. It's the name given to the lightning storm that occurred during the Pythagorean calendar period (the 8th century BCE) in ancient Greece, which is characterized by rapid rain and loud thunder.