Bb 13sus4, 5th inversion (G in the bass)
Also written as Bb13sus4/G.
Notes, from the bass up
G (bass)A#D#E#G#B#
The same notes as Bb 13sus4 (G, A#, D#, E#, G# and B#), rearranged so G is the lowest note. Use it to move between chords with smaller jumps across the keyboard.