Longman Dictionary of Contemporary English - improvise

~ v 1 to do something without any preparation, because you are forced to do this by unexpected events  (I forgot to bring the notes for my speech, so I just had to improvise.) 2 to make something by using whatever you can find because you do not have the equipment or materials that you need  (We improvised a crude shelter using branches.) 3 to perform music, drama or comedy that comes straight from your imagination and has never been performed before  (You can't be a good jazz musician if you can't improvise.) - improvisation n