Fleeting means gone almost as soon as it is noticed. A fleeting glimpse, fleeting moment, fleeting pleasure.
It suggests brevity with a touch of regret, which is why it attaches to glimpses, smiles, moments and fame rather than to meetings. A fleeting thought is one that passes before it can be caught. It is a slightly literary word and none the worse for it. Note fleetingly; and that it comes from an old verb meaning to float or drift away, which is also where the fleet of ships comes from.
1adjectivefleetingGone almost as soon as it is noticed.
“We caught a fleeting glimpse of the fox before it vanished into the trees.”
fleeting is a quality of brevity.
Middle English fleten meant to float or drift, from Old English fleotan. A fleet of ships is the same root — things that float — so a fleeting moment is one that floats past.
Proto-Indo-European
*plewd-
Proto-Germanic
*fleutaną
Old English
flēotan — to float
Middle English
fleten — to float
English, today
fleeting
From Middle English fleten (“to float”), from Old English flēotan (“to float”), from Proto-Germanic fleutaną, from Proto-Indo-European plewd-. by surface analysis, fleet + -ing.
Etymology from Wiktionary, CC BY-SA