The phrase "turns on steam" typically refers to the act of heating or powering up a machine or device, such as a steam engine or boiler. Antonyms for this phrase include "shuts off steam," "turns off power," "disables heating," or "deactivates machinery." These terms all suggest a cessation or reduction of energy and/or motion, rather than an increase. Other possible antonyms could include "turns down the heat," "puts a damper on energy," or "unplugs the machinery," depending on the specific context and meaning of the phrase. By exploring different antonyms, we can gain a deeper understanding of the nuances and implications of the original phrase.