Great Britain vs high tea

Great Britain and high tea both are nouns.

Word	Noun	Adjective	Verb	Adverb
Great Britain	Yes	No	No	No
high tea	Yes	No	No	No

Great Britain (noun)	high tea (noun)
an island comprising England and Scotland and Wales	substantial early evening meal including tea
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