Tomahawk Sweep

A guard-bottom sweep against a standing opponent that attacks one ankle and sends uke falling to the side rather than straight back. Tori hooks behind one of uke's ankles or heels with their same-side arm (the "tomahawk" arm), while the other hand controls uke's opposite knee, hip, or collar. Tori opens the guard, sits up at an angle, and chops their controlling arm diagonally across the body - the motion that gives the technique its name — driving uke off-balance toward the attacked corner. Uke falls to one side, and tori comes up to pass or directly to mount.

Mechanically the tomahawk sits between the lumberjack sweep (both ankles, straight backward) and the ankle pick (single ankle, standing). It's the closed-guard analog of an ankle pick: same single-leg-removal principle, executed from underneath.