Yes, this is like doing the "I'm a little teapot" dance you did as a kid. With your feet roughly hip-width apart, hold the weight plate or medicine ball directly above your head with your elbows slightly bent.

While keeping the weight plate or ball directly above your head, lean your body laterally to one side and shift your hips to the opposite side until you feel a mild stretch.

Reverse the motion and repeat, leaning your torso and hips to the opposite direction without pausing in the middle between reps.

Related:  Dynamic Training for Abs & Obliques

Related:  The Misinterpreted Ab Training Study