What is Sidecar?
1.
Anyone who is in a relationship/partnership who is clearly not wearing the metaphorical trousers, or in more extreme cases, only worked with/dated by the other for superficial reasons I.E - money or looks, and while everyone else can see this, they cannot.
Good looking woman walks into a crowded bar and pushes her way to the front, and without asking the small nerdy guy on HER arm what he wants, she orders the drinks.
ONLOOKER 1: "woah check out that blonde!"
ONLOOKER 2: "...check out the sidecar"
See
2.
technique of manually stimulating the female genitals with two fingers in the vagina and slipping a pinky into the anus
While Jane was enjoying the dexterity of my index and forefinger I slipped in a sidecar for the win.