C 7alt, 3rd inversion (Db in the bass)
Also written as C7alt/Db.
Notes, from the bass up
Db (bass)D#AbCEBb
The same notes as C 7alt (Db, D#, Ab, C, E and Bb), rearranged so Db is the lowest note. Use it to move between chords with smaller jumps across the keyboard.