Definition of "ephemeral"

Esteem, lasting esteem, the esteem of good men, like himself, will be his reward, when the gale of ephemeral popularity shall have gradually subsided.

1821-1822, Vicesimus Knox, Remarks on the tendency of certain Clauses in a Bill now pending in Parliament to degrade Grammar Schools

sentences not of ephemeral, but of eternal, efficacy

1853, James Stephen, Lecture on the right use of Books

It was during an access of this kind that I suddenly left my home, and bending my steps towards the near Alpine valleys, sought in the magnificence, the eternity of such scenes, to forget myself and my ephemeral, because human, sorrows.

1818, Mary Shelley, chapter 9, in Frankenstein‎, archived from the original on 3 April 2012

The graben constitutes a depositional basin and a topographic low, underlain by Cretaceous shales, in which volcanic debris accumulated in ephemeral lakes and streams in Oligocene and early Miocene time.

1986, W.H. Raymond, "Clinoptilolite Deposit in the Pine Ridge Indian Reservation, South Dakota, U.S.A.", in Yūichi Murakami et al. (editors), New Developments in Zeolite Science and Technology (conference proceedings), Elsevier, page 80