C sharp suspended fourth flat ninth piano chord - C#b9sus
The C sharp suspended fourth flat ninth chord is a 5-note chord consisting of the notes C#, F#, G#, B and D.
You can see these notes highlighted in the interactive piano chart below.
The chord itself is often abbreviated as C#b9sus.
Interactive piano diagram for the C sharp suspended fourth flat ninth chord
Chords that are a subset of C#b9sus. These contain less notes but all of them are included in C#b9sus.