Fleeting

From Middle English fleten ("to float"), from Old English flÄ“otan ("to float").

Full definition of fleeting

1931, Martha Kinross, "The ScreenÂ â€” From This Side", The Fortnightly, Volume 130, page 511:Architecture, sculpture, painting are static arts. Even in literature "our flying minds," as George Meredith says, cannot contain protracted description. It is so; for from sequences of words they must assemble all the details in one simultaneous impression. But moments of fleeting beauty too transient to be caught by any means less swift than light itself are registered on the screen.
2003, Gabrielle Walker, Snowball Earth: The Story of a Maverick Scientist and His Theory of the Global Catastrophe That Spawned Life As We Know It, Three Rivers Press (2003), ISBN 1400051258, pages 34-35: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.
2008, Barbara L. Bellman & Susan Goldstein, Flirting After Fifty: Lessons for Grown-Up Women on How to Find Love Again, iUniverse (2008), ISBN 9780595428281, page 12: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.
2010, Leslie Ludy, The Lost Art of True Beauty: The Set-Apart Girl's Guide to Feminine Grace, Harvest House Publishers (2010), ISBN 9780736922906, page 5:And I am inspired afresh to pursue the stunning beauty of Christ rather than the fleeting beauty of this world.

fleeting