The Collaborative International Dictionary of English v.0.48:

Quenchless \Quench"less\, a.
   Incapable of being quenched; inextinguishable; as, quenchless
   fire or fury. "Once kindled, quenchless evermore." --Byron.
   [1913 Webster]

   Syn: Inextinguishable; unquenchable.
        [1913 Webster] -- Quench"less*ly, adv. --
        Quench"less*ness, n.
        [1913 Webster]