Christmas cake vs Great Britain

Christmas cake and Great Britain both are nouns.

Word	Noun	Adjective	Verb	Adverb
Christmas cake	Yes	No	No	No
Great Britain	Yes	No	No	No

Christmas cake (noun)	Great Britain (noun)
a rich fruitcake (usually covered with icing and marzipan) and eaten at Christmas	an island comprising England and Scotland and Wales
	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