Dawn Raid
This is a market term used to describe the situation in which one company or stockbroker working on behalf of a corporate client launches a sudden surprise buying campaign in the stockmarket.
Such a move is often the prelude to a formally announced bid - it is an attempt by the bidding company (the predator) to build a substantial stake in its target (the victim) at the prevailing stockmarket price (which is likely to be significantly lower than the price at which it would need to make a formal takeover bid).