A subprocess, also called a subflow, is a flow rule that is referenced in another flow rule, so that execution of the other rule may start execution of the subprocess. For example, this flow references a subprocess identified as Specialist Underwriting:
Add a Subprocess shape to start another flow and temporarily pause processing of the current flow, a form of branching or "call with return". The second flow is called a subprocess of the first flow. The subprocess icon marks the shape.
The Split For Each shape, Spinoff, and Split Join shapes also "call" subprocesses.
The calling flow — that contains the Subprocess, Spinoff, Split For Each or Split Join shape — is known as the parent flow. This is a runtime or dynamic designation, because many different flows can branch or call a common subprocess.