*cathetus*

‖n.; pl. catheti [ L., fr. Gr. &unr_; a perpendicular line, fr. &unr_; let down, fr. &unr_;. See Catheter. ] (Geom.) One line or radius falling perpendicularly on another; as, the catheti of a right-angled triangle, that is, the two sides that include the right angle. Barlow. [ 1913 Webster ]