Pertaining to operation that is independent of any other device, program, or system.

A standalone device is able to function independently of other hardware. This ...

A program, function or system that operates on its own and has no interfaces.

A device or system that can perform its function independently.

A computer system which can function independently of any other computer system or device. TUV

A computer capable of functioning by itself, as opposed to being a terminal of another computer.

This refers to any kind of device that functions without the use of other components, for example a PC that is not networked.