C11 chord

The C dominant eleventh chord (abbreviated C11 chord) is a six-note chord consisting of the notes C, E, G, B♭, D, and F. The chord is formed by adding an eleventh to the C dominant ninth chord.

In practice, the third (E) and fifth (G) are often omitted from the C11 chord to avoid a very dissonant sound, and because it's not always possible to play all notes simultaneously.