wall wart

wall wart
 n.

   A small power-supply brick with integral male plug, designed to plug
   directly into a wall outlet; called a `wart' because when installed on
   a power strip it tends to block up at least one more socket than it
   uses. These are frequently associated with modems and other small
   electronic devices which would become unacceptably bulky or hot if
   they had power supplies on board (there are other reasons as well
   having to do with the cost of UL certification).