Source : Webster's Revised Unabridged Dictionary (1913)

Metachrosis \Met`a*chro"sis\, n. [NL., from Gr. ? beyond + ? a
   coloring.] (Biol.)
   The power og changing color at will by the expansion of
   special pigment cells, under nerve influence, as seen in many
   reptiles, fishes, etc. --Cope.