An ominous sign is a warning of something bad that is about to happen. It can be a physical sign, such as a dark cloud or a strange noise, or it can be a more abstract sign, such as an OMEN or an AUGURY. The crossword solutions for the term 'ominous sign' are 'POTENT, ' 'AUGURY, ' 'OMEN, ' and 'warcloud.' These words all refer to signs that indicate something bad is about to happen. POTENT means powerful or influential, and it can refer to a sign that has a strong impact on the people who witness it. AUGURY is a sign from the gods that predicts the future, and OMEN is a sign of bad luck. Finally, warcloud is a dark cloud that symbolizes impending danger.