From Longman Dictionary of Contemporary Englishquadrilateralquad‧ri‧lat‧er‧al /ˌkwɒdrəˈlætərəl◂ $ ˌkwɑː-/ noun [countable] technical HMCFa flat shape with four straight sides —quadrilateral adjective
Examples from the Corpus
quadrilateral• For emotional resonance, flags are about as potent as a quadrilateral of cloth can be.• The cyclic quadrilateral so formed has an important property; its opposite angles add to 180°.• The cluster is made up of a small quadrilateral which is distinctive enough, and is very characteristic with × 20. 