Unquenchable

Adjective

 * 1) That which cannot be quenched.
 * After running 12 miles in the hot sun his thirst appeared to be unquenchable.

Thesaurus
a hog for, acquisitive, all-devouring, avaricious, avid, bottomless, coveting, covetous, deathless, devouring, esurient, gluttonous, gobbling, grabby, grasping, greedy, hoggish, immortal, imperishable, impregnable, incorruptible, indelible, indestructible, ineffaceable, ineradicable, inexpugnable, inextinguishable, insatiable, insatiate, invincible, invulnerable, irrepressible, limitless, mercenary, miserly, money-hungry, money-mad, nonperishable, omnivorous, overgreedy, piggish, quenchless, rapacious, ravening, ravenous, slakeless, sordid, swinish, unappeasable, unappeased, undampable, undestroyable, undying, unsated, unsatisfiable, unsatisfied, unslakeable, unslaked, venal, voracious