quarter. [planar form with four sides] tetract†, tetragon, quadrangle, rectangle. [three dimensional object with four surfaces] tetrahedron. quadrature, quadrifoil, quadriform, quadruplet; quatrefoil. [object or animal with four legs] tetrapod. [geographical area with four sides] quadrangle, quad [Coll.]. [electromagnetic object] quadrupole. [four fundamental studies] quadrivium. V. reduce to a square, square. Adj. four; quaternary, quaternal†; quadratic; quartile; tetract†, tetractic†, tetractinal†; tetrad, tetragonal; square, quadrate.