Rectilineal \Rec`ti*lin"e*al\ (-l?n"?*al), Rectilinear \Rec`ti*lin"e*ar\ (-l?n"?*?r), a. [Recti- + lineal, linear.] Straight; consisting of a straight line or lines; bounded by straight lines; as, a rectineal angle; a rectilinear figure or course. -- {Rec`ti*lin"e*al*ly}, adv. -- {Rec`ti*lin"e*ar*ly}, adv.