United Kingdom of Great Britain and Northern Ireland vs copper's nark

United Kingdom of Great Britain and Northern Ireland and copper's nark both are nouns.

Word	Noun	Adjective	Verb	Adverb
United Kingdom of Great Britain and Northern Ireland	Yes	No	No	No
copper's nark	Yes	No	No	No

United Kingdom of Great Britain and Northern Ireland (noun)	copper's nark (noun)
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	an informer or spy working for the police