Bb Major 7#11, 4th inversion (E in the bass)
Also written as Bbmaj7#11/E.
Notes, from the bass up
E (bass)A#DE#A
The same notes as Bb Major 7#11 (E, A#, D, E# and A), rearranged so E is the lowest note. Use it to move between chords with smaller jumps across the keyboard.