stand-alone

/S T AE1 N D AH0 L OW0 N/
noun
  1. 1

    A device that can operate on its own, rather than as an accessory for another device.

  2. 2

    (by extension) Something that is not a part of some series or sequence.

adjective
  1. 1

    Operating, functioning, or existing without additions or assistance; independent; able to be separate or separated.

    โ€œThey offer an inexpensive add-on for a computer, or a stand-alone system with all the functions built in.โ€

Source: https://en.wiktionary.org/wiki/stand-alone