fleeting
FLEE-tingadjMeaning passing very quickly
Memory hook FLEE-ting: it FLEES before you look. Kai turns, and the fox flees into the trees: one flash of orange tail, and it is gone. His look at it was fleeting.
Kai caught a fleeting glimpse of the fox before it vanished into the trees.
In context The sun appeared for only a fleeting moment between the clouds, just long enough for the hikers to see the valley below.
Similar brief, momentary, passing, quick
Opposite lasting, long, enduring
From the old verb fleet, “to glide away swiftly.”