Tet"ra*gon (?), n. [L. tetragonum, Gr. ; (see Tetra-) + corner, angle: cf. F. t'etragone.]
A plane figure having four sides and angles; a quadrangle, as a square, a rhombus, etc.
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.
© Webster 1913.