A unit of energy in the MKS system (meter-kilogram-second). Pronounced just like "jewel," a joule is equal to 10,000,000 ergs in the CGS (centimeter-gram-second) system. Surge protectors are often given joule ratings, but this refers only to the amount of energy they can absorb, not how much gets through. See
MKS system,
CGS system and
J/T.