What is "greater fool theory"

n. (context economics English) The theory of making money by buying something for the sole reason of selling it to someone else for a higher price.

The greater fool theory states that the price of an object is determined not by its intrinsic value, but rather by irrational beliefs and expectations of market participants. A price can be justified by a rational buyer under the belief that another party is willing to pay an even higher price. In other words, one may pay a price that seems "foolishly" high because one may rationally have the expectation that the item can be resold to a "greater fool" later.