Standalone is spelt either closed or hyphenated (stand-alone) which roughly translates to the state of being independent. It is used to describe a machine that doesn't rely on other peripherals to work effectively.
"Netflix announced that they would create a free standalone live streaming service in the US on Monday."
Stand alone means to stay in your own league/class apart from others. If someone stands alone, they are superior in terms of skill, power, speed and talent than any other person for that field.
"Cristiano Ronaldo stands alone as the best player in the history of Football."