*fugacious*

a. [ L. fugax, fugacis, from fugere: cf. F. fugace. See Fugitive. ] 1. Flying, or disposed to fly; fleeing away; lasting but a short time; volatile. [ 1913 Webster ]

Much of its possessions is so hid, so fugacious, and of so uncertain purchase. Jer. Taylor. [ 1913 Webster ]

2. (Biol.) Fleeting; lasting but a short time; -- applied particularly to organs or parts which are short-lived as compared with the life of the individual. [ 1913 Webster ]