The word "fitter" is usually used to describe someone who is physically fit and healthy. However, there are a variety of synonyms that can be used in place of this word. These synonyms range from more formal and specific terms, such as "athlete" and "gymnast," to more casual and general terms like "health enthusiast" and "fitness buff." Other synonyms for "fitter" may include "exerciser," "stronger," "healthier," or "more agile." Ultimately, the choice of synonym depends on the specific context and intended meaning, but with the aforementioned words, a writer can expand their vocabulary and make their writing more interesting.