Reverse-biased usually refers to how a
diode is used in a
circuit. If a diode is reverse biased, the voltage at the cathode is higher than that at the anode. Therefore, no current will flow until the diode breaks down. This effect is used to one's advantage in
zener diode regulator circuits. Zener diodes have a certain - low - breakdown voltage. A standard value for breakdown voltage is for instance 5.6V. This means that the voltage at the cathode can never be more than 5.6V higher than the voltage at the anode, because the diode will break down - and therefore conduct - if the voltage gets any higher. This effectively regulates the voltage over the diode. Here is how a simple zener regulation circuit would look: For more information, refer to
Zener diode.
See more at Wikipedia.org...
a voltage placed across a junction in the reverse direction. When a junction is reverse biased, current flow is blocked until the junction breaks down.