1. Denoting something which comes up all of a sudden at the moment and unexpectedly: Guests suddenly arrived at Alice's home in the evening, so an extemporary meal had to be prepared with what was currently available because there was no time to go shopping for any additional food.
2. Regarding something made for, or suggested by the occasion; hastily built, prepared, or provided: Tom's town decided to put up an improvised or extemporary housing for the refugees which were expected during the following two weeks.