one of those large transformer blocks that usually comes with many consumer electronics, and usually takes up more than one plug, because it's so big
Unplug that wall wart right now, before your mother sees you
A giant plastic goober that sticks to the wall, most often near a power outlet. Such a device is used to provide low-intensity power for critical equipment including, but not limited to:
-Game Boy with dead batteries
-Radio Controlled Ankle Grinders (in the form of car, truck, battlebot, etc)
-Mobile gaming station (known also as a Notebook Computer)
NB: in the case of the mobile gaming station, the wart is usually relocated halfway up the cord, rather than being plugged directly into the wall.
1)I lost the wall wart for my phone, so I've been making a lot of collect calls lately.
2)I keep dropping stuff behind the sofa, because the wall wart keeps me from putting the sofa against the wall.