Great Britain vs pothouse

Great Britain and pothouse both are nouns.

Word	Noun	Adjective	Verb	Adverb
Great Britain	Yes	No	No	No
pothouse	Yes	No	No	No

Great Britain (noun)	pothouse (noun)
an island comprising England and Scotland and Wales	tavern consisting of a building with a bar and public rooms; often provides light meals
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