jiffy
     n : a very short time (as the time it takes the eye blink or the
         heart to beat); "if I had the chance I'd do it in a
         flash" [syn: {blink of an eye}, {flash}, {heartbeat}, {instant},
          {split second}, {trice}, {twinkling}, {wink}, {New York
         minute}]
Source: WordNet® 2.0

jiffy n. 1. The duration of one tick of the system clock on your
   computer (see {tick}). Often one AC cycle time (1/60 second in the U.S.
   and Canada, 1/50 most other places), but more recently 1/100 sec has
   become common. "The swapper runs every 6 jiffies" means that the virtual
   memory management routine is executed once for every 6 ticks of the
   clock, or about ten times a second. 2. Confusingly, the term is
   sometimes also used for a 1-millisecond {wall time} interval. 3. 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_. 4. Indeterminate time from a few seconds to
   forever. "I'll do it in a jiffy" means certainly not now and possibly
   never. This is a bit contrary to the more widespread use of the word.
   Oppose {nano}. See also {Real Soon Now}.


Source: The Jargon File