Glossary of Judo terminology
In Judo, the term "Stun" refers to a Shime waza (Strangling techniques) or an Atemi-waza (Vital-point striking technique) which causes the opponent to lose consciousness.
An opponent whose neck is being strangled may lose consciousness if he resists.
Atemi-waza (Vital-point striking technique) in which a combatant strangles the opponent with any part of his body are both hazardous and forbidden due to the powerful strangling force they apply.
Moreover, the Sankaku-jime (Triangular strangle) and the Kansetsu waza (Joint locks) are forbidden in junior divisions up to and including the junior high school level. At the high school level, the referee may render a judgment if the Waza is deemed effective.