平面曲线 píngmiànqūxiàn plane curve Origin Definitions Defs Strokes Stroke Words Sentences Sents 平面 píngmiàn noun plane (geometry) a flat surface; in mathematics, a surface containing all the straight lines that connect any two points on it曲线 曲線 qūxiàn noun curve a curved line; (geometry) the trajectory of a moving point