B Minor Major 9th, 3rd inversion (A# in the bass)
Also written as Bm(maj9)/A#.
Notes, from the bass up
A# (bass)C#BDF#
The same notes as B Minor Major 9th (A#, C#, B, D and F#), rearranged so A# is the lowest note. Use it to move between chords with smaller jumps across the keyboard.