diagramn.[Gr. , fr. to mark out by lines; dia` through + to draw, write: cf. F. diagramme. See Graphic.]1. (Geom.) A figure or drawing made to illustrate a statement, or facilitate a demonstration; a plan.()2. Any simple drawing made for mathematical or scientific purposes, or to assist a verbal explanation which refers to it; a mechanical drawing, as distinguished from an artistical one.()Indicator diagram. (Steam Engine) See Indicator card, under indicator()v. t. To put into the form of a diagram.()