A failure of equipment to operate properly due to electrons being unable to leap through the atmosphere from a male plug to a female connector.
"Was the reason that fixture wouldn't come on an air-gap?"
"Yeah, it accidentally got unplugged."
This entry inspired by
http://www.controlbooth.com/forums/g...one-short.html.
Not to be confused with
spark-gap or
arc-gap, which are real, actual things.