What is Bear Raid?

Legal Definition
A bear raid is a type of stock market strategy, where a trader (or group of traders) attempts to force down the price of a stock to cover a short position. The name is derived from the common use of bear or bearish in the language of market sentiment to reflect the idea that investors expect downward price movement.

A bear raid can be done by spreading negative rumors about the target firm, which puts downward pressure on the share price. This is typically considered a form of securities fraud. Alternatively, traders could take on large short positions themselves, manipulating the price with the large volume of selling, making the strategy self-perpetuating.
-- Wikipedia
Legal Definition
When traders drive down prices of a security. Its illegal. Refer to prearranged trading.