When a founder or group of founders take code that is useless by itself, from their former products, stick it together, and make a prototype/product that is incredibly popular.
Macgyverism is a term used to denote taking seemingly useless things to make something incredible.
Jimmy's new iOS game, Chang goes to India, was a result of macgyverist product development where he took a bunch of useless code from his previous projects, stuck it together in an hour, and shipped it.