a bar that reinforces the frame of a car, esp one used for racing, rallying, etc, to protect the driver if the car should turn over
Collins Concise English Dictionary © HarperCollins Publishers::
roll′ bar′,
- Automotivea heavy steel transverse bar in the form of an inverted
U rising from the framework of an automobile to prevent its occupants from being crushed if the vehicle rolls over.
- 1950–55