The Collaborative International Dictionary
Quadrantal triangle
Quadrantal \Quad*ran"tal\, a. [L. quadrantalis containing the fourth fourth part of a measure.] (Geom.) Of or pertaining to a quadrant; also, included in the fourth part of a circle; as, quadrantal space.
Quadrantal triangle, a spherical triangle having one side equal to a quadrant or arc of 90[deg].
Quadrantal versor, a versor that expresses rotation through one right angle.