1) Ephemeral 2) Fleeting 3) French word used in English 4) Fugacious 5) Fugitive 6) Impermanent 7) Lasting a very short time 8) Momentary 9) Passing 10) Short-lived 11) Temporary 12) Transient Found on https://www.crosswordclues.com/clue/transitory
Marked by the quality of passing away: evanescent, transient, of brief duration: existing momentarily: temporary. ... (18 Nov 1997) ... Found on http://www.encyclo.co.uk/local/20973