" extemporary "

1: made or done without previous thought or preparation;

  * e.g., " ... caught red-handed, the would-be embezzler proceeded to give some extemporary and not very convincing explanations for her actions "

•  Synonyms : 

•  ad hoc,

•  ad-lib,

•  down and dirty,

•  extemporaneous,

•  extempore,

•  impromptu,

•  improvisational,

•  improvised,

•  off-the-cuff,

•  offhand,

•  offhanded,

•  snap,

•  spur-of-the-moment,

•  unconsidered,

•  unplanned,

•  unpremeditated,

•  unprepared,

•  unrehearsed,

•  unstudied

•  Antonyms : 

•  considered,

•  planned,

•  premeditated,

•  premeditative,

•  prepared,

•  rehearsed