An electrical component that allows electricity to flow only one way. Used in the rectifier bridge of an alternator
. Also used as L.E.D. (light emitting diode) lights.
Dumbass: "The guys at the parts store tested my alternator and said that the diodes are bad. How much to replace them?"
Guy at alternator rebuilders shop: "Those rank amatures don't know what they're talking about, and neither do you, you dumb ass."