All these great 'f' words =) =)
fugacious \fyoo-GAY-shuhs\ adjective:
: lasting but a short time; fleeting
The fugacious nature of life and time.
--Harriet Martineau, Autobiography
[T]astes, smells... being, in comparison, fugacious.
--John Stuart Mill, Examination of Sir W. Hamilton's Philosophy
When he proposed the tax in May, Altman thought it would follow the fugacious nature of some flowers: bloom quickly and die just as fast.
--Will Rodgers, "Parks proposal falls on 3-2 vote," Tampa Tribune, June 27, 2001
Fugacious is derived from Latin fugax, fugac-, "ready to flee, flying; hence, fleeting, transitory," from fugere, "to flee, to take flight." Other words derived from the same root include fugitive, one who flees, especially from the law; refuge, a place to which to flee back (re-, "back"), and hence to safety; and fugue, literally a musical "flight."
BTW, here's my Interesting Words List if you want to see what other WOTD's I liked enough to keep.