Source : Webster's Revised Unabridged Dictionary (1913)

Quadrangular \Quad*ran"gu*lar\, a. [Cf. F. quadrangulaire.]
   Having four angles, and consequently four sides; tetragonal.
   -- {Quad*ran"gu*lar*ly}, adv.

Source : WordNet®

quadrangular
     adj : of or relating to or shaped like a quadrangle