Tet″ra‐gon (?), n. [L. tetragonum, Gr. τετράγωνον; τέτρα- (see Tetra-) + γωνία corner, angle: cf. F. tétragone.] 1. (Geom.) A plane figure having four sides and angles; a quadrangle, as a square, a rhombus, etc.
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.