Ab Dominant 13th, 4th inversion (A# in the bass)
Notes, from the bass up
A# (bass)C#E#G#B#D#F#
The same notes as Ab Dominant 13th (A#, C#, E#, G#, B#, D# and F#), rearranged so A# is the lowest note. Use it to move between chords with smaller jumps across the keyboard.