Diminished major seventh chord

In music theory, a diminished major seventh chord is a seventh chord composed of a diminished triad and a major seventh. Thus, it is composed of a root note, together with a minor third, a diminished fifth, and a major seventh above the root: (1, ♭3, ♭5, 7).

Source: Wikipedia — Diminished major seventh chord (CC BY-SA 4.0)