The definition of evanescent is something fleeting that passes out of sight or mind quickly.
An example of evanescent is a rainbow that appears for only a moment after a storm.
tending to pass away or fade from sight like mist or smoke; ephemeral
Origin of evanescent; from Classical Latin evanescens, present participle : see evanesce
Vanishing or likely to vanish like vapor.
(comparative more evanescent, superlative most evanescent)