extemporize vs extemporise

extemporize and extemporise both are verbs.

Word	Noun	Adjective	Verb	Adverb
extemporize	No	No	Yes	No
extemporise	No	No	Yes	No

As verbs, extemporize and extemporise are synonyms defined as:

Other synonyms of extemporize include ad-lib, improvise, improvize.

extemporize (verb)	extemporise (verb)
perform without preparation	perform without preparation
manage in a makeshift way; do with whatever is at hand