What is "superfluous interval"

Superfluous \Su*per"flu*ous\, a. [L. superfluus overflowing; super over, above + fluere to flow. See Super-, and Fluent.] More than is wanted or is sufficient; rendered unnecessary by superabundance; unnecessary; useless; excessive; as, a superfluous price.
--Shak.

An authority which makes all further argument or illustration superfluous.
--E. Everett.

Superfluous interval (Mus.), an interval that exceeds a major or perfect interval by a semitone.

Syn: Unnecessary; useless; exuberant; excessive; redundant; needless. [1913 Webster] -- Su*per"flu*ous*ly, adv. -- Su*per"flu*ous*ness, n.

n. (context music English) An interval that exceeds a major or perfect interval by a semitone.