Tumidness is a relatively uncommon word that typically refers to swelling or bloating. If you're looking for synonyms, there are several options to choose from. For instance, the word "edema" is often used to describe swelling caused by retained fluids in the tissues. "Bloating" is another common synonym, particularly when referring to abdominal distention. "Inflammation" is another term that can be used to describe tumidness, as it refers to the body's response to injury or infection, which may result in swelling. "Swelling" itself is also a useful synonym, as it describes the enlargement of a particular body part or area due to an accumulation of fluid or tissue.