MREM is a unit of measurement for radiation exposure. It stands for millirem, which is a smaller unit of rem. However, there are other synonyms that can be used interchangeably with the term MREM. For instance, mSv is a metric unit that is widely used in Europe, while R is a traditional unit that is commonly used in the United States. Both units measure the amount of radiation that is absorbed by the body. It is essential to note that synonyms for MREM are just different ways of expressing the same thing. Regardless of the unit used, they all have the same meaning and purpose of measuring radiation exposure.