A plan, sketch, drawing, or outline designed to demonstrate or explain how something works or to clarify the relationship between the parts of a whole.
Mathematics A graphic representation of an algebraic or geometric relationship.
A chart or graph.
tr.v.
di·a·grammed or di·a·gramed, di·a·gram·ming or di·a·gram·ing, di·a·grams To indicate or represent by or as if by a diagram.
[Latin diagramma, figure, from Greek, a figure worked out by lines, plan, from diagraphein, to mark out, delineate : dia-, dia- + graphein, to write; see gerbh- in Indo-European roots.] di'a·gram'ma·ble adj., di'a·gram·mat'ic (-grə-māt'ĭk), di'a·gram·mat'i·cal adj., di'a·gram·mat'i·cal·ly adv.
[dahy-uh-gram] 
noun, verb, -gramed or -grammed, -gram⋅ing or -gram⋅ming.
əˌgræm