to tailgate: To drive as close as possible behind another driver, without any concern for the obvious danger involved in the situation. If the driver in front had to slam on their brakes, the driver behind would have no chance to stop. Collision.

The tailgater is probably tailgating under the impression that driving dangerously close will cause the driver in front to speed up. Never give in to a tailgater, as this will only encourage them to continue their dangerous habit.