Wiktionary
n. 1 (context music English) a minor key with the notes C, D, E♭, F, G, A♭, B♭ 2 (context music English) the minor chord with a root of C
Wikipedia
C minor (abbreviated c or Cm) is a minor scale based on C, consisting of the pitches C, D, E, F, G, A, and B. The harmonic minor raises the B to B. Changes needed for the melodic and harmonic versions of the scale are written in with naturals and accidentals as necessary.
Its key signature consists of three flats. Its relative major is E-flat major, and its parallel major is C major.
Usage examples of "c minor".
Well, if Rachmaninoff could do the same thing with the C Minor Concerto, why shouldn't he?
The cymbals in Beethoven's head had stopped, the piccolo too, and all that was left was the droning of the bassi in the trio of the C Minor Symphony, that grotesque dance toward Hell.