Term Definition: Task
Main Description

A Task is an atomic activity that is included within a Process. A Task is used when the work in the Process is not broken down to a finer level of Process detail. Generally, an end-user and/or an application are used to perform the Task when it is executed. A Task object shares the same shape as the Sub-Process, which is a rectangle that has rounded corners.

This term can be found in the OMG  Business Process Model and Notation, V2.0 specification http://www.omg.org/spec/BPMN/2.0/PDF/