Source : Webster's Revised Unabridged Dictionary (1913)

Rectangular \Rec*tan"gu*lar\ (r?k*t?n"g?*l?r), a. [CF. F.
   rectangulaire.]
   Right-angled; having one or more angles of ninety degrees. --
   {Rec*tan"gu*lar*ly} (r?k*t?n"g?*l?r*l?), adv. --
   {Rec*tan"gu*lar*ness}, n.