As a Noun: 1. The moving, doing or happening of something very quickly. English = speed, rapidity. 2. The act of moving very fast in a vehicle, usually a car, so that you are over the legal speed limit. English = speeding. As a Verb or Adjective: 1. To move, do something, or happen with great speed or very quickly. English = (be) fast, go fast, rush, speed.