Great Britain vs dicky-seat

Great Britain and dicky-seat both are nouns.

Word	Noun	Adjective	Verb	Adverb
Great Britain	Yes	No	No	No
dicky-seat	Yes	No	No	No

Great Britain (noun)	dicky-seat (noun)
an island comprising England and Scotland and Wales	a small third seat in the back of an old-fashioned two-seater
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