Source : Webster's Revised Unabridged Dictionary (1913)

Achromatism \A*chro"ma*tism\, n. [Cf. F. achromatisme.]
   The state or quality of being achromatic; as, the achromatism
   of a lens; achromaticity. --Nichol.

Source : WordNet®

achromatism
     n : the visual property of being without color [syn: {colorlessness},
          {colourlessness}] [ant: {color}]