Subtonic

• POS: Noun
• HYPHEN: sub=ton=ic

CIDE DICTIONARY

Subtonic, a. 

 Applied to, or distinguishing, a speech element consisting of tone, or proper vocal sound, not pure as in the vowels, but dimmed and otherwise modified by some kind of obstruction in the oral or the nasal passage, and in some cases with a mixture of breath sound; -- a term introduced by Dr. James Rush in 1833. See Guide to Pronunciation, 1913 Webster]

Subtonic, n. 

•  A subtonic sound or element; a vocal consonant, as b, d, g, n, etc.; a subvocal.  [1913 Webster]
•  The seventh tone of the scale, or that immediately below the tonic; -- called also subsemitone.  [1913 Webster]

OXFORD DICTIONARY

Subtonic, n. Mus. the note below the tonic, the seventh note of the diatonic scale of any key.