Although the doctors had been able to 'keep her illness at bay' [=to prevent her illness from becoming worse] for a few months, the disease soon began to spread again.
Armed with a gun, he 'held the police at bay' [=he did not allow the police to arrest him] for 10 hours.
The soldiers 'kept the attackers at bay'. [=they did not allow the attackers to come closer]
(..) We are taking over the ship. Aye! Avast! This ship cannot be crewed by two men. You'll never make it out of the bay. Son, I'm Captain Jack Sparrow. Savvy? Commodore. LT.GILLETTE: Sir, they've taken the Dauntless! (..)2003 Pirates of the Caribbean: The Curse of the Black Pearl