Definition of 'Minsky Moment'
When a market fails or falls into crisis after an extended period of market speculation or unsustainable growth. A Minsky moment is based on the idea that periods of speculation, if they last long enough, will eventually lead to crises; the longer speculation occurs the worse the crisis will be. This crisis is named after Hyman Minsky, an economist and professor famous for arguing the inherent instability of markets, especially bull markets. He felt that long bull markets only ended in large collapses.
Investopedia explains 'Minsky Moment'
The phrase "Minsky moment" was coined by Paul McCulley in 1998 while referring to the Asian Debt Crisis of 1997, in which speculators put increasing pressure on dollar-pegged Asian currencies until they eventually collapsed. These types of crises occur because investors take on additional risk during prosperous times or bull markets. The longer a bull market lasts, the more risk is taken in the market. Eventually, so much risk is taken that instability ensues.
For example an investor might borrow funds to invest while the market is in an upswing. If the market drops slightly, leveraged assets might not cover the debts taken to acquire them. Soon after, lenders start calling in their loans. Speculative assets are hard to sell, so investors start selling less speculative ones to take care of the loans being called in. The sale of these investments causes an overall decline in the market. At this point, the market is in a Minsky moment. The demand for liquidity might even force the country's central bank to intervene.