jiffy
1. The duration of one {tick} of the computer's {system
clock}. Often one AC cycle time (1/60 second in the US and
Canada, 1/50 most other places), but more recently 1/100 sec
has become common.
2. Confusingly, the term is sometimes also used for a
1-millisecond {wall time} interval. Even more confusingly,
physicists semi-jokingly use "jiffy" to mean the time required
for light to travel one foot in a vacuum, which turns out to
be close to one ▫nanosecond▫.
[{Jargon File}]