'No bail' is a term used in the criminal justice system as well as in correctional facilities as a pre-trial custody status.
When a defendant is held in a no bail status, his or her ability to post bond in any amount is prohibited. To be held without bail usually means that the defendant exhibited conduct which, by contemporary standards, was shocking to the conscience of the court. Or, the judge or prosecutor in the case had divine insight into the defendant's guilt prior to adjudication of the matter, and the court argued that the defendant posed a significant flight risk or threat to the community.
It's common for a person held in custody on a 'no bail' status to feel really and truly fucked. It's a prudent business practice to place the subject on a suicide watch while he or she is a resident of the correctional facility awaiting trial.