1. (Science: geometry) 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.
(Science: engineering) see indicator card, under indicator
Origin: gr, fr. To mark out by lines; through – to draw, write: cf. F. Diagramme. See graphic.