Source : Webster's Revised Unabridged Dictionary (1913)

Indefatigably \In`de*fat"i*ga*bly\, adv.
   Without weariness; without yielding to fatigue; persistently.
   --Dryden.

Source : WordNet®

indefatigably
     adv : with indefatigable energy; "she watched the show
           indefatigably" [syn: {tirelessly}, {inexhaustibly}]