extemporaneous (adj.)
- ad-lib
- casual
- extemporary
- extempore
- haphazard
- hasty
- impromptu
- improvised
- impulsive
- informal
- jury-rigged
- makeshift
- off-the-cuff
- offhand
- precipitate
- rough-and-ready
- spontaneous
- spur-of-the-moment
- surprised
- uncontrived
- unhatched
- unmade
- unorganized
- unplanned
- unpremeditated
- unprepared
- unready
- unrehearsed
- unstudied
