Source : Webster's Revised Unabridged Dictionary (1913)

Unmeasurable \Un*meas"ur*a*ble\, a.
   Immeasurable. --Swift. -- {Un*meas"ur*a*ble*ness}, n. --
   {Un*meas"ur*a*bly}, adv.

Source : WordNet®

unmeasurable
     adj : impossible to measure; "unmeasurable reaches of outer space"
           [syn: {immeasurable}, {immensurable}] [ant: {measurable}]