Co jest steam? Co jest steam? 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.