over a barrel

over a barrel also over the barrel  {adv. phr.},  {informal}

In the power of your enemies; not able to do anything about what happens to you; in a helpless condition; trapped.

Bill had Tom over a barrel because Tom owed him money.

Ralph has me over a barrel; I need five dollars, and he won't lend it to me unless I let him use my bicycle.

Compare: ON THE ROPES.