||Cath"e*tus (?), n.; pl. catheti (#). [L., fr. Gr. &?; a perpendicular line, fr. &?; let down, fr. &?;. 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.