The phrase "low key" is often used to describe a situation that is casual, relaxed, or not very intense. However, there are many other synonyms for this term that can be used to convey similar meanings. Some examples of synonyms for low key include understated, muted, subdued, restrained, low-profile, subtle, modest, and toned-down. These words are often used in conversations or writing to express a sense of calmness or simplicity. Additionally, low key can be used to describe an individual's demeanor or behavior in a particular situation, such as when someone is being reserved or playing it cool. Overall, low key is a versatile term that can be replaced by many different synonyms depending on the context and tone of the communication.