n. [ L. tetragonum, Gr. tetra`gwnon; te`tra- (see Tetra-) + gwni`a corner, angle: cf. F. tétragone. ] 1. (Geom.) A plane figure having four sides and angles; a quadrangle, as a square, a rhombus, etc. [ 1913 Webster ]

2. (Astrol.) An aspect of two planets with regard to the earth when they are distant from each other ninety degrees, or the fourth of a circle. Hutton. [ 1913 Webster ]

a. 1. (Geom.) Of or pertaining to a tetragon; having four angles or sides; thus, the square, the parallelogram, the rhombus, and the trapezium are tetragonal fingers. [ 1913 Webster ]

2. (Bot.) Having four prominent longitudinal angles. [ 1913 Webster ]

3. (Crystallog.) Designating, or belonging to, a certain system of crystallization; dimetric. See Tetragonal system, under Crystallization. [ 1913 Webster ]