impromptu
     adj : 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" [syn:
            {ad-lib}, {extemporaneous}, {extemporary}, {extempore},
            {offhand}, {offhanded}, {off-the-cuff}, {unrehearsed}]
     n 1: an extemporaneous speech or remark; "a witty impromptu must
          not sound premeditated"
     2: a short musical passage that seems to have been made
        spontaneously without advance preparation
     adv : without advance preparation; "he spoke ad lib" [syn: {ad lib},
            {ad libitum}, {spontaneously}]
Source: WordNet® 2.0