slipping hand under opponent's arm to grab belt
Sumo technique where a wrestler reaches under the opponent's arm and grips the back of the belt (mawashi).
If your slipping hand is caught, you'll be at a disadvantage.
He attacked decisively from the slipping-hand grip.
A sumo compound of 差し, the continuative form of 差す in the sense of inserting an arm, and 手, “hand.”