Great Britain vs L-plate

Great Britain and L-plate both are nouns.

Word	Noun	Adjective	Verb	Adverb
Great Britain	Yes	No	No	No
L-plate	Yes	No	No	No

Great Britain (noun)	L-plate (noun)
an island comprising England and Scotland and Wales	a square plate bearing the letter L that is attached to both ends of a car to indicate that the driver is a learner
a monarchy in northwestern Europe occupying most of the British Isles; divided into England and Scotland and Wales and Northern Ireland; `Great Britain' is often used loosely to refer to the United Kingdom