The vapor phase of water. A mist of cooling water vapor. Pressurized water vapor used for heating, cooking, or to provide mechanical power. The power produced by a machine using pressurized water vapor. Steam heating. Power; energy. To produce or emit steam. To become or rise up as steam. To become misted or covered with steam. To move by means of steam power. Informal To become very angry; fume. To expose to steam, as in cooking.