get behind phrasal verb ( see also ↑ get )
1 . if you get behind with a job, payments, rent etc, you do not do or pay as much of it as you should have by a particular time
get behind with
I don’t want to get behind with my work.
You can always catch up later if you get behind.
2 . get behind somebody informal to support someone:
The crowd really got behind them and cheered them on.