Source : Webster's Revised Unabridged Dictionary (1913)

Inextinguishable \In`ex*tin"guish*a*ble\, a.
   Not capable of being extinguished; extinguishable;
   unquenchable; as, inextinguishable flame, light, thirst,
   desire, feuds. ``Inextinguishable rage.'' --Milton.

Source : WordNet®

inextinguishable
     adj : difficult or impossible to extinguish; "an inextinguishable
           flame"; "an inextinguishable faith" [ant: {extinguishable}]