Made, done, furnished, or procured at the time, without special preparation; resulting from or provided for the immediate occasion; unpremeditated: as, an extemporaneous address or performance; extemporaneous support or shelter.Synonyms Extemporaneous, Unpremeditated. There is now some disposition to apply extempore and extemporaneous to that which is unpremeditated only in form. Extemporaneous speaking or preaching is, by this view, carefully prepared in thought, arrangement, etc., only the choice of words and phraseology being left to the inspiration of the moment. Extemporary has not this sense. Unpremeditated is thus opposed to premeditated, and extemporaneous to written or recited.In pharmacy, noting a preparation which is compounded at the time it is ordered, in distinction from a ready-made, or officinal preparation.