DDoS

Short for Distributed Denial of Service, DDoS is a type of DoS attack that uses several computers to attack one victim. Often a DDoS attack is first done by hacking or infecting dozens, hundreds, or even thousands of other computers with instructions on when to attack and how; when that time arises, all infected computers attack at once. A DDoS is often needed to attack a big site that is capable of handling large ammounts of traffic.

Also see: Botnet, DoS, Security definitions, Zombie