Source : Webster's Revised Unabridged Dictionary (1913)

Dichromatism \Di*chro"ma*tism\, n.
   The state of being dichromatic.

Source : WordNet®

dichromatism
     n : a deficiency of color vision in which the person can match
         any given hue by mixing only two other wavelengths of
         light (as opposed to the three wavelengths needed by
         people with normal color vision) [syn: {dichromacy}, {dichromatopsia},
          {dichromia}, {dichromasy}]