A short is borrowing stock to sell, promising to re-buy that stock in the future to give back to the lender. The stock price can rise arbitrarily high, which me

A short is borrowing stock to sell, promising to re-buy that stock in the future to give back to the lender. The stock price can rise arbitrarily high, which means you may have to pay an arbitrarily high price to re-purchase the stock in the future. See "short squeeze" and read about the Volkswagen/Porsche example a couple years back.