Noun
(geometry, non-Euclidean geometry) The amount by which the total of the interior angles of a triangle is less than 180° (π radians); the amount by which the total of the internal angles of a polygon is less than what would be expected on the Euclidean plane.
(geometry) The amount by which the total of the angles around a vertex of a polyhedron is less than 360° (2π radians).
(dentistry, periodontics) The angular displacement of a tooth from vertical.
Source: en.wiktionary.org