G Minor Major 9th, 1st inversion (Bb in the bass)
Also written as Gm(maj9)/Bb.
Notes, from the bass up
Bb (bass)DF#AG
The same notes as G Minor Major 9th (Bb, D, F#, A and G), rearranged so Bb is the lowest note. Use it to move between chords with smaller jumps across the keyboard.