Evil Cart is a weed cartridge that was/turned evil and now feast's on people who hits it causing the person to turn evil or overdose.
John: yo look at this cart i got!
Mike: why does the cart look evil?
John: I dont know but its fine!
"SEVERAL HOURS LATER"
John: i think you were right that carts evil!
Mike: ....
John: are you okay?
Mike: *Evil noises"
John: Shit!
John: now thats cart is a Evil Cart!
An Evil Cart refers to an exceptionally potent/powerful cart. Users of an Evil Cart can potentially green out relatively quickly.
Yo Jeff let me hit his Evil Cart yesterday and I was gone for the whole day!