This term has been covered by the website Wikipedia as "Improvisation"
This mediawiki site, a `wiki dictionary` about the nature and practice of free improvisation declines to duplicate the complete content of that listing. Below there is an introduction - a simple copy and paste. from Wikipedia then a link to the Wikipedia entry.
Introduction, copied from Wikipedia
Improvisation is the activity of making or doing something not planned beforehand, using whatever can be found.
Improvisation in the performing arts is a very spontaneous performance without specific or scripted preparation. The skills of improvisation can apply to many different faculties, across all artistic, scientific, physical, cognitive, academic, and non-academic disciplines; see Applied improvisation.
Improvisation also exists outside the arts. Improvisation in engineering is to solve a problem with the tools and materials immediately at hand. Improvised weapons are often used by guerrillas, insurgents and criminals.