A type of scale with the 3rd, 6th, and 7th notes lowered by one semitone, with the interval pattern:
tone - semitone - tone - tone - semitone - tone - tone.
Starting on the note C, this produces a scale with the notes C, D, E♭, F, G, A♭, B♭, C:
{c'd'es'f'g'aes'bes'c''}