jiffy vs split second

jiffy and split second both are nouns.

Word	Noun	Adjective	Verb	Adverb
jiffy	Yes	No	No	No
split second	Yes	No	No	No

As nouns, jiffy and split second are synonyms defined as:

jiffy and split second: a very short time (as the time it takes the eye to blink or the heart to beat)

Other synonyms of jiffy include blink of an eye, flash, heartbeat, instant, New York minute, trice, twinkling, wink.

jiffy (noun)	split second (noun)
a very short time (as the time it takes the eye to blink or the heart to beat)	a very short time (as the time it takes the eye to blink or the heart to beat)