From Longman Dictionary of Contemporary EnglishL-plateL-plate /ˈel pleɪt/ noun [countable] TTCa flat white square with a red letter L on it, that must be attached to the car of someone who is learning to drive in Britain → P-plate
Examples from the Corpus
L-plate• Residents say too many learner drivers are taking lessons in their streets, and now they want the L-plates moved on. 