What is the meaning of Windshield_wiper?

a device used to clear rain and dirt from a windshield; normally a pivoting arm with a rubber blade

An exercise where the back is parallel to the ground (lying on it or hanging via the arms from a pull-up bar) and the legs are perpendicular to the floor so that the lower torso with the legs is rotated to target the Musculus obliquus externus abdominis, the Musculus quadratus lumborum and the Musculus rectus abdominis.

Source: wiktionary.org