"Fleeting beauty" refers to something that is beautiful but only for a short period of time. It implies that the beauty is temporary and will not last forever. Full definition
Her striking black and white photographs create fragmented images that express fleeting beauty and the turbulence of contemporary life. (galerielelong.com)
Peter Doig paints scenes I wish I had seen, capturing the instantaneous and fleeting beauty of the ordinary that we know can be extraordinary if we are lucky enough to see it as such. (bampfa.org)
Pine trees laugh in the face of cold, trees in grasslands have very thick bark to resist fires, some plants in the tundra have dish - like flowers that chase the sun to collect as much warmth as they can, and then some plants only bloom once a year, as if to remind us of just how fleeting beauty can be. (thedressedaesthetic.com)