in·com·men·su·ra·ble (nk-mnsr--bl, -shr-)

1.
a. Impossible to measure or compare.
b. Lacking a common quality on which to make a comparison.
2. Mathematics
a. Having no common measure or number of which all the given lengths or measures are integral multiples.
b. Having an irrational ratio.

Adj. 1. incommensurable - impossible to measure or compare in value or size or excellence
incomparable, uncomparable - such that comparison is impossible; unsuitable for comparison or lacking features that can be compared; "an incomparable week of rest and pleasure"; "the computer proceeds with its incomparable logic and efficiency"; "this report is incomparable with the earlier ones because of different breakdowns of the data"
2. incommensurable - not having a common factor
incommensurate - (often followed by `with') not corresponding in size or degree or extent; "a reward incommensurate with his effort"

http://www.thefreedictionary.com/incommensurable