Japanese art of self-defense. It employs locks and holds and utilizes the principle of nonresistance to cause an opponent's own momentum to work against him or her. Aikido emphasizes the importance of achieving complete mental calm and control of one's own body to master an opponent's attack. There are no offensive moves. It traces its origins to Japanese martial (samurai) traditions dating to the 14th century, and it was developed as a modern form in the early 20th century by Ueshiba Morihei. Seemartial art.