*tetragonal*

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 ]