insatiable

Not satiable; incapable of being satisfied or appeased; very greedy.

Hugo, in a fine frenzy, threatens to depose the Sacristan, to do this and do that; but, in the mean while, how to quiet your insatiable Jew? Hugo, for this couple of hundreds, grants the Jew his bond for four hundred payable at the end of four years. (...) Neither yet is this insatiable Jew satisfied or settled with: he had papers against us of 'small debts fourteen years old;' his modest claim amounts finally to 'Twelve hundred pounds besides interest'

Such an appointment would realize my fondest dreams. But no, at any sacrifice, I must set bounds to my insatiable ambition!

One who or that which cannot be satiated.