Aikido
Aikido (合気道; "Way of unifying spirit") is a Japanese martial art created by Morihei Ueshiba in the early 20th century from Aikijutsu and Jujutsu, specifically Daito-ryu aikijujutsu.
It is somewhat similar to judo in that it uses throws and locks, but it focuses more on defense than offense, including defenses against attacks by armed attackers, such as knives and nunchaku. As a result, high-level practitioners are able to defend themselves effectively against even simultaneous attacks by multiple opponents.
Randori is a term used in Japanese martial arts to describe free-style sparring. The term denotes an exercise involving a random succession of uke attacks. In aikido, especially in the Aikikai school of aikido, it refers to a form of practice in which a defender defends against multiple attackers in rapid succession without knowing how they will attack or in what order.