Describing a lens or optical system tilted toward the viewer's face at the bottom, allowing the eye to transition smoothly between distant viewing through the upper half and near viewing through the lower half. This tilt optimizes the optical center for downward gaze angles. It minimizes peripheral distortion and aberrations when shifting focus.
Heard on the job
Increase the pantoscopic tilt by a few degrees to eliminate the glare they're getting off the lower rim.