Source : Webster's Revised Unabridged Dictionary (1913)

Incommensurable \In`com*men"su*ra*ble\, a. [Pref. in- not +
   commensurable: cf. F. incommensurable.]
   Not commensurable; having no common measure or standard of
   comparison; as, quantities are incommensurable when no third
   quantity can be found that is an aliquot part of both; the
   side and diagonal of a square are incommensurable with each
   other; the diameter and circumference of a circle are
   incommensurable.

         They are quantities incommensurable.     --Burke.
   -- {In`com*men"su*ra*ble*ness}, n. -- {In`com*men"su*ra*bly},
   adv.

Incommensurable \In`com*men"su*ra*ble\, n.
   One of two or more quantities which have no common measure.

Source : WordNet®

incommensurable
     adj 1: impossible to measure or compare in value or size or
            excellence
     2: not having a common factor