'Supertonic' definitions:

Definition of 'supertonic'

(from WordNet)
noun
(music) the second note of a diatonic scale

Definition of 'Supertonic'

From: GCIDE
  • Supertonic \Su`per*ton"ic\, n. (Mus.) The note next above the keynote; the second of the scale. --Busby. [1913 Webster]