Great Britain vs bubble and squeak

Great Britain and bubble and squeak both are nouns.

Word	Noun	Adjective	Verb	Adverb
Great Britain	Yes	No	No	No
bubble and squeak	Yes	No	No	No

Great Britain (noun)	bubble and squeak (noun)
an island comprising England and Scotland and Wales	leftover cabbage fried with cooked potatoes and sometimes meat
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