1) Something you flip, push, press or generally use to change things around you, for example turning a light on or off, turning on a computer, changing the settings of a washing machine, whatever. 2) A verb related to the above action of flipping/pushing. 3) Also a synonym of change.
To be a bitch, and talk in a derogative about someone in front on their face, and then start talking to them as normal, complementing them excessively, to cover up the hurtful comments.
That girl Sarah is such a Switch, the way she was speaking to Holly like that and then complemented her like nothing even happened.
You know you're a slut but your hair looks nice and you post good pictures on Instagram !