Fugacious

Fugacious \fyoo-GAY-shuhs\ , adjective;
1. Lasting but a short time; fleeting

This word entered the language around 1630 with the meaning "fleeing, likely to flee." It comes from Latin fugaci-, which is the stem of fugax. Fugax means "apt to flee, timid," but figuratively it's more like "transitory, fleeting" and comes from fugere + -ous ("to flee" + "having, full of, having to do with, doing, inclined to"). Fugere is also the forebear of fugitive and derives from the Proto-Indo-European base *bheug ("to flee").

Today's word and the first definition were both taken from Dictionary.com's 'Word of the Day' for Tuesday, March 22
Etymologies come from the Oxford English Dictionary and/or Etymonline.com