"Steaming up" is a phrase that typically describes a situation where something becomes foggy or cloudy due to rising steam or heat. Some antonyms for this phrase could include words such as clearing, airing, or cooling down. These words suggest the opposite of steam building up and indicate that the situation is becoming clearer or more comfortable. For example, if a car windshield is steaming up, the driver might need to clear it so they can see more clearly. Alternatively, if a person feels hot and bothered, they might need to take a moment to cool down and feel more comfortable.