(1) A graphical implementation of an activity, including actions, execution flow, and external calls. An activity diagram contains symbols that specify the steps, the order of the steps, and the logic that determines how they execute. See also activity.
(2) A diagram that represents the performance of a task or duty in a workflow, or the execution of a statement in a procedure.
(3) See activity graph.
(4) A UML behavioral diagram that models the dynamic parts of a system by showing the steps or tasks that constitute a process.