The Collaborative International Dictionary of English v.0.48:
Quadrangular \Quad*ran"gu*lar\, a. [Cf. F. quadrangulaire.] Having four angles, and consequently four sides; tetragonal. -- Quad*ran"gu*lar*ly, adv. [1913 Webster]WordNet (r) 3.0 (2006):
quadrangular adj 1: of or relating to or shaped like a quadrangle