Final answer:
In a Data Flow Diagram (DFD), the symbol depicted with a circle is known as a "process" node. This symbol represents the transformation or manipulation of data within the system modeled.
Step-by-step explanation:
The symbol in a Data Flow Diagram (DFD) that is usually portrayed with a circle is called a process node. The process is one of the key elements in a DFD and is used to represent a transformation or manipulation of data within the system being modeled. Processes can be anything from simple calculations to complex operations that handle various data inputs and outputs. For example, a process might represent the calculation of sales tax on a transaction in a market for goods and services or the processing of wages and salaries in the labor market.