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"fleeting" is also used as a crossword clue. If that's what you saw, the answer is often momentary (9 letters).
Definitions
lasting for a markedly brief time
Word origin
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.
Used in a sentence
“During the fleeting summer months of his field season, when the outer vestiges of winter melted briefly, there were ponds and pools and lakes of water everywhere.”
“For starters, we see examples all the time of some middle-aged men trying to hang onto their own fleeting youth by sporting younger women on their arms.”
“And I am inspired afresh to pursue the stunning beauty of Christ rather than the fleeting beauty of this world.”
Source: Wiktionary, CC BY-SA 4.0
Used as a crossword answer2 curated clues
01“Very brief”8 letters
02“Briefly passing”8 letters
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