Little paddles on a rotating spindle - usually used to move a liquid - sometimes air etc.
On a dishwasher the drain pump impeller can be found under a simple cover at the very bottom of the sump inside the washing cabinet.
If you take the cover off (usually just one screw) you will see the impeller - sometimes jammed by lemon pips etc. The impeller should rotate freely but with a bit of magnetic resistance.
Peccavi, October 2010
