Definition of diminished seventh
1 : a musical interval (see interval sense 2c)that is smaller than a seventh by a semitone
2 or diminished seventh chord : a seventh chord that is often built on the leading tone, that spans the interval (see interval sense 2c)of a diminished seventh (sense 1), and that consists of three minor thirds
— called also diminished chord
— see seventh chordKeep scrolling for more
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Merriam-Webster unabridgedWords at Play
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Time Traveler for diminished seventh
The first known use of diminished seventh was in 1753
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