The bear trap is a sudden downward price movement that entices bearish investors to sell an investment short, followed by a price reversal back upward. As prices rise, short sellers lose money, which may trigger a margin call or force them to cover their position by buying back borrowed shares.
Bear traps are caused by a drop in price below a key support level, not just downtrends. A break downward through a resistance level is expected to result in further downward movement by bearish investors or traders. After the price reversal back upward, they are "trapped" and lose money.