The B flat dominant flat ninth chord is a 5-note chord consisting of the notes Bb, D, F, Ab and Cb.
You can see these notes highlighted in the interactive piano chart below.
The chord itself is often abbreviated as Bb7b9.
Interactive piano diagram for the B flat dominant flat ninth chord
Chords that are a subset of Bb7b9. These contain less notes but all of them are included in Bb7b9.