四し角かく形けいしかくけいFreq.FrequencyTop 50,000Meanings1nounquadrilateral; quadrangle; tetragongeometryGeometric term for any four-sided polygon. The reading しかっけい is a common colloquial variant.正せい方ほう形けいは四し角かく形けいの一いっ種しゅです。A square is a type of quadrilateral.