n. (Geom.) An instrument for drawing curved lines. [ 1913 Webster ]
{ } a. [ L. curvus bent + E. lineal, linear. ] Consisting of, or bounded by, curved lines; as, a curvilinear figure. [ 1913 Webster ]
n. The state of being curvilinear or of being bounded by curved lines. [ 1913 Webster ]
adv. In a curvilinear manner. [ 1913 Webster ]