British spelling vs improvise

British spelling is a noun but improvise is not a noun.

Word	Noun	Adjective	Verb	Adverb
British spelling	Yes	No	No	No
improvise	No	No	Yes	No

British spelling (noun)	improvise (noun)
English orthography used in the UK, Ireland and most of the Commonwealth (characterized by 'analyse', 'centre' and 'useable')

British spelling (verb)	improvise (verb)
	perform without preparation
	manage in a makeshift way; do with whatever is at hand