One is faced with imminent danger or trouble. In Greek mythology, the courtier Damocles was forced to sit beneath a sword suspended by a single hair to emphasize the instability of a king's fortunes. I know his history of violent behavior, so I feel like a sword of Damocles is hanging over my head whenever I'm alone with him. With the threat of nuclear war, many feel that the sword of Damocles hangs over the world's head like never before.