(1) any of several variously named and variously defined anatomic angles that have been used to quantify facial protrusion; (2) in dentistry, the angle formed by the intersection of the orbitomeatal (Frankfort) plane with the nasion-pogonion line (inner lower angle), which establishes the anteroposterior relation of the mandible to the upper face at the orbitomeatal plane. SYN: Frankfort-mandibular incisor angle.