The derogatory term "mewler" is commonly used to describe someone who complains or whines excessively. However, there are many other words that can be used to describe this behavior. Some synonyms for "mewler" include crybaby, whiner, complainer, grumbler, and moaner. Other options include bellyacher, griper, sniveler, and kvetcher. While these words may seem harsh, they can be used in a humorous manner or to describe someone who is truly annoying with their constant complaining. It's important to remember that everyone has a bad day from time to time, but constant negativity can be draining on those around us.