Short Selling

Borrowing and selling an asset you do not own, betting the price will fall.

Short selling involves borrowing shares from a broker and selling them at the current price, with the intent to repurchase them later at a lower price and pocket the difference. If the price rises instead, the short seller faces potentially unlimited losses. Requires a margin account.

Betting the overpriced stock would fall, he made money short selling it before the earnings miss.