Double Flat

A note lowered in pitch by two semitones, sounding enharmonically a whole step lower. So, an Ebb sounds the same pitch as a D. Double flats are generally used to indicate accidentals in a flat key or altered pitches in a chord; for example, a flat 9 in the key of Ab would be spelled Bbb, while a flat 5 in a Gb min 7 chord would be spelled Dbb. Yes, you could spell that Dbb as a C, but it makes the chord harder to recognize and a C technically would be interpreted as a #11, which indicates a different flavor for soloing and accompaniment.