Source : Webster's Revised Unabridged Dictionary (1913)

Immensurable \Im*men"su*ra*ble\, a. [Pref. im- not + L.
   mensurabilis measurable: cf. F. immensurable. Cf.
   {Immeasurable}.]
   Immeasurable.

         What an immensurable space is the firmament. --Derham.

Source : WordNet®

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