Can someone tell me what "quashing the indictment" means?

Answer 1

The first answer is correct.

An indictment is a formal charge -- often rendered by a grand jury (depending on the rules of the jurisdiction). It is basically an order for the prosecution to proceed.

Quashing is a legal term meaning to declare a previous order or decision ineffective -- to nullify it. Used most often for subpoens but also for indictments.

Answer 2

"Quashing" is equivalent in meaning to "dismissing" the indictment. The indictment is gone.

Answer 3

To set aside or annul the indictment.