1.
If you hang back , you move or stay slightly behind a person or group, usually because you are nervous about something.
I saw him step forward momentarily but then hang back, nervously massaging his hands.
PHRASAL VERB : V P
2.
If a person or organization hangs back , they do not do something immediately.
They will then hang back on closing the deal...
Even his closest advisers believe he should hang back no longer.
PHRASAL VERB : V P on n , V P