From WordNet (r) 3.0 (2006) :
blink of an eye
n 1: a very short time (as the time it takes the eye to 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, jiffy, split second, trice, twinkling,
wink, New York minute]