adjective
composed, devised, or done at the moment rather than beforehand
made an extemporaneous speech after the dinner
Synonyms: autoschediastic, extemporary, extempore, impromptu, improvised, offhand, spur-of-the-moment, unrehearsed, unstudied; compare unintentional
Related Word: casual, informal; unprepared, unthought-out; impulsive, snap, spontaneous
Idioms: off the cuff, on the spur of the moment
Contrasted words: designed, planned, prepared, projected, schemed, thought-out; considered, deliberated, premeditated, studied