temporary expedient vs improvisation

temporary expedient and improvisation both are nouns.

Word	Noun	Adjective	Verb	Adverb
temporary expedient	Yes	No	No	No
improvisation	Yes	No	No	No

As nouns, temporary expedient and improvisation are synonyms defined as:

temporary expedient (noun)	improvisation (noun)
an unplanned expedient	an unplanned expedient
	a performance given extempore without planning or preparation
	a creation spoken or written or composed extemporaneously (without prior preparation)