Definition of "tetragonal" [te•trag•o•nal]

• Having four sides (as a tetragon); quadrilateral. (adjective)
• Having two equal axes and one unequal, and all angles 90°. (adjective)

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• "Rutile is made up mostly of titanium dioxide with two rarer polymorphs anatase or octahedrite, which is a tetragonal mineral of pseudo-octahedral habit, and brookite, which is an orthorhombic mineral, the Doctor explained to her."
• "Such an organism would draw not a triangle-based color-wheel but a tetragonal color-sphere."
• "One of the most arresting pictures is Karl Benjamin's 1957 oil-on-linen "Small Planes: White, Blue, and Pink," whose multiple tetragonal shapes look like boxes that have been mounted, or spread, but simultaneously seem to float weightlessly on the picture plane."