MEGA-MEGA is a term used to describe something that is extremely LARGE or powerful. It is derived from the Greek prefix 'mega, ' which means 'GREAT' or 'LARGE.' The term is often used to describe something that is beyond the normal scope of size or power. For example, a mega-mall would be an extremely LARGE shopping center, and a mega-computer would be a powerful computer with more processing power than a typical computer.