The Collaborative International Dictionary of English v.0.48:
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. [1913 Webster]