Jodan Oyayubi Ipponken is a technique in Kyokushin karate. It translates to 'Upper-Level Thumb One-Knuckle Fist.' This technique involves forming a fist where the thumb presses against the base of the index finger, creating a single-knuckle striking surface, aimed at the opponent's upper body or head. The term 'Jodan' refers to the upper level, 'Oyayubi' indicates thumb, and 'Ipponken' denotes one-knuckle fist. It is commonly used for close-range strikes to vulnerable areas such as the face, jawline, or temple.