EXTEMPORARY

extemporaneous, ad-lib, extemporary, extempore, impromptu, offhand, offhanded, off-the-cuff, unrehearsed

(adjective) with little or no preparation or forethought; “his ad-lib comments showed poor judgment”; “an extemporaneous piano recital”; “an extemporary lecture”; “an extempore skit”; “an impromptu speech”; “offhand excuses”; “trying to sound offhanded and reassuring”; “an off-the-cuff toast”; “a few unrehearsed comments”

Source: WordNet® 3.1

Adjective

extemporary (comparative more extemporary, superlative most extemporary)

Extemporaneous.

Source: Wiktionary

Ex*tem"po*ra*ry, a.

1. Extemporaneous. "In extemporary prayer." Fuller.

2. Made for the occasion; for the time being. [Obs.] "Extemporary habitations." Maundrell.

Source: Webster’s Unabridged Dictionary 1913 Edition