What is Ambulatory Will?

Legal Definition
A changeable will (ambulatoria voluntas), the phrase denoting the power which a testator possesses of altering his will during his life-time. See Hattersiey v. Bis-sett, 50 N. J. Eq. 577, 25 Atl. 332
-- Black's Law Dictionary
Legal Definition
the right a testator has that enables them to change a will.