Final answer:
The process that involves constant volume in a piston-cylinder device is called isochoric process, also known as isovolumetric process.
Step-by-step explanation:
The process that involves constant volume in a piston-cylinder device is called isochoric process, also known as isovolumetric process.
In an isochoric process, the volume of the system remains constant, while other properties such as pressure and temperature can change.
This process occurs when the piston is fixed in its position, and no work is performed by or on the system.