What is the meaning of the word "l-plate"?

Definitions:

  1. A square plate bearing the letter 'L' that is attached to both ends of a car to indicate that the driver is a learner. copy to clipboard NOUN
  2. A square, white sign with a red letter 'L' on it, attached to the back and the front of a vehicle that is being driven by a person learning to drive. copy to clipboard NOUN