\Te*trag"o*nal\, 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.

2. (Bot.) Having four prominent longitudinal angles.

3. (Crystallog.) Designating, or belonging to, a certain
   system of crystallization; dimetric. See {Tetragonal
   system}, under {Crystallization}.