josh jam

Tendency of a publicly traded market, such as a stock market, to rise shortly before the market closes (in a manner that is at once surprising yet somehow predictable). The adjective presumably comes from the American colloquial "josh", as in "joke" or "it happened again so you must be joking", and "jam" as in a supply of buying orders that overwhelms the selling pressure on the market.

The Dow 30 got another josh jam, up +30 in the last few minutes - that's the third day in a row!