Greater Fool Theory

What Does Greater Fool Theory Mean?
A theory that states it is possible to make money by buying securities, whether overvalued or not, and later selling them at a profit because there will always be someone (a bigger or greater fool) who is willing to pay the higher price.

Investopedia explains Greater Fool Theory
When acting in accordance with the greater fool theory, an investor buys questionable securities without any regard to their quality, but with the hope of quickly selling them off to another investor (the greater fool), who might also be hoping to flip them quickly. Unfortunately, speculative bubbles always burst eventually, leading to a rapid depreciation in share price due to the selloff.