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TETRAGONAL
1. 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. Having four prominent longitudinal angles.
3. Designating, or belonging to, a determined system of crystallization; dimetric. See Tetragonal system, under Crystallization.
Source: Websters Vocabulary