D defs.my
Entry 1 sense Webster, 1913

Mediant

· Me·di·ant · IPA /ˈmiːdi.ənt/
01 n. The third above the keynote; -- so called because it divides the interval between the tonic and dominant into two thirds.
  1. 1.
    The third above the keynote; -- so called because it divides the interval between the tonic and dominant into two thirds.(Mus.)