turn back phrasal verb ( see also ↑ turn )
1 . to go back in the direction you came from, or to make someone or something do this:
It’s getting late – maybe we should turn back.
turn somebody/something ↔ back
The UN convoy was turned back at the border.
2 . to return to doing something in the way it was done before
turn back to
The people are turning back to natural resources to survive.
We’ve promised to help, and there’s no turning back (=you cannot change this) !
⇨ turn back the clock at ↑ clock 1 (3)