蹲踞 (Sonkyo or Sonko) is a way of sitting by squatting down or kneeling down on the knees to lower the hips.
蹲う (Tsukubau) means bowing to the ground and 踞む (Kogomu) means bending down, sitting down or crouching, and therefore the combination of these two characters can represent the posture of bowing politely with one's body bended down that is taken to show respect toward any person of high rank passing by.
For sumo or kendo (Japanese fencing), sonkyo refers to the posture taken by the wrestlers or the fighters as they face each other and squat down at each starting line, just prior to the start of a match.
For sumo, it means squatting with the buttocks on the raised heels, the knees apart, and the upper body straight.
For kendo, it refers to the same posture as for sumo, or the posture of kneeling down on one knee with the upper body straight. Sometimes, sonkyo is executed holding a shinai (bamboo sword) with the point aimed at the opponent's eyes. In traditional kenjutsu (swordplay), the proper posture called orishiki was executed by kneeling down with one knee next to the other foot, but in kendo, a new posture executed by raising heels with the buttocks on them was established.
Sonkyo is also a posture executed in religious services of Shinto or other Japanese religions, and is further a way of sitting for a samurai retainer waiting for any order. In this case, the knees are put together, which is different from sonkyo for sumo and the like.