Great Britain vs copper's nark

Great Britain and copper's nark both are nouns.

Word	Noun	Adjective	Verb	Adverb
Great Britain	Yes	No	No	No
copper's nark	Yes	No	No	No

Great Britain (noun)	copper's nark (noun)
an island comprising England and Scotland and Wales	an informer or spy working for the police
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