A sump pump is a (usually) a metal
powered mechanism used for pumping water
(or some other liquid of similar consistency
Many of these pumps are designed for tasks such as keeping a basement
dry, or generally keeping water below a certain level. As such, they often have buoyant
attachments which, when they float
above a certain level, automatically activate the pump.
A sump pump usually has a plastic hose which is attached to it, and this carries the water out to it's destination (e.g., somewhere besides the basement.)
At the moment, I'm sitting in an inundated basement, which unfortuneately happens to contain my computer and cable modem, and a sump pump is the only thing keeping me from being totally submerged.