(colloquial) A very short, unspecified length of time.
1913, Joseph C. Lincoln, Mr. Pratt's Patients Chapter 7, Old Applegate, in the stern, just set and looked at me, and Lord James, amidship, waved both arms and kept hollering for help. I took a couple of everlasting big strokes and managed to grab hold of the skiff's rail, close to the stern. Then, for a jiffy, I hung on and fought for breath.
I'll be back in a jiffy.
(computing) A unit of time defined by the frequency of its basic timer; historically, and by convention, 0.01 seconds, but some operating systems use other values.
(electronics) The time between alternating current power cycles (1/60 or 1/50 of a second)
(physics) The time taken for light to travel one centimetre in a vacuum (sometimes one foot, or sometimes the width of a nucleon)
