He dwelt a great deal on the fleetingness of life, and the wisdom of making the best of its few charming things.
It was a little transient ray that had been sent athwart her darkness, and no one understood its fleetingness better than did she.
The fleetingness of all earthly things vividly occurred to him.
I am afraid I was not overwhelmed with thoughts of the fleetingness of life or the horror of death.
early 13c., "fickle, shifting, unstable," from Old English fleotende "floating, drifting," later "flying, moving swiftly," from present participle of fleotan (see fleet (v.)). Meaning "existing only briefly" is from 1560s.