l-plate

from WordNet (r) 3.0 (2006)

L-plate
    n 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

from The Collaborative International Dictionary of English v.0.48

L-plate \L-plate\ n.
   a square plate bearing the letter L that is attached to both
   ends of a car to indicate that the driver is a learner.
   [British]
   [WordNet 1.5]