prison guard
jailer
jailor
gaoler
screw *
turnkey

He was watched all the time by a prison guard.

Go out there and watch her like a prison guard?

The prison guard looked the two court officers up and down.

Among the 42 active cases were one prison guard and two health care workers.

Even the prison guards did not know who he was.

Then he saw that three of the men weren't prison guards.

The prison guards wrote a letter in support as well.

There were two prison guards on the other side of the security door.

Ask a prison guard what it's like to try and control half a dozen.

The prison guard went to some trouble to cover up the abuse.