A jiffy can mean several different time intervals:

A short period of time or a moment. The origin of the word is unknown, but is believed to have first appeared in 1779.

In computing, the duration of one tick of the system timer interrupt. Typically, this time is 0.01 seconds.

In physics, the time taken for light to travel one centimetre (sometimes one foot, or sometimes the width of a nucleon)

In electronics, the time between alternating current power cycles (1/60 or 1/50 of a second) - see alternating current

An indeterminate amount of time from a few seconds to forever.

this last is how my dad used it, "I'll be home in a jiffy, Dear."

edit: btw, at the link mav gave, for time, you'll find 'shake' and 'wink'; but no jiffy.