adjective Operating, functioning, or existing without additions or assistance; independent; able to be separate or separated; not attached to anything.
They offer an inexpensive add-on for a computer, or a stand-alone system with all the functions built in.
adjective Not part of a series, or not requiring familiarity with that series.
a stand-alone sequel
noun A device that can operate on its own, rather than as an accessory for another device.
noun Something that is not a part of some series or sequence.