Synonyms:
- ad-lib,
- be caught napping,
- be surprised,
- be taken unawares,
- be unprepared,
- cook up,
- dash off,
- do offhand,
- fake,
- go off half-cocked,
- have no plan,
- improvisate,
- improvise,
- jury-rig,
- knock off,
- lash up,
- make up,
- play by ear,
- scrap the plan,
- strike off,
- throw off,
- throw together,
- toss off,
- toss out,
- vamp,
- whip up,
- whomp up,
- wing it