Definitions for "Mediant"
Keywords:  tonic, iii, keynote, diatonic, triad
The third above the keynote; -- so called because it divides the interval between the tonic and dominant into two thirds.
the note or chord on the third degree of the major scale. Often marked with the Roman numeral III.
(music) the third note of a diatonic scale; midway between the tonic and the dominant