Synonyms for impromptu

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impromptu is applied to that which is spoken, made, or done on the spur of the moment to suit the occasion and stresses spontaneity; extemporaneous, extempore (more commonly used as an adverb), and extemporary may express the same idea but are now more often used of a speech that has received some preparation, but has not been written out or memorized; improvised applies to something composed or devised without any preparation and, with reference to things other than music, suggests the ingenious use of whatever is at hand to fill an unforeseen and immediate need