A mumbler can also be referred to as a mutterer, whisperer, or inarticulate speaker. They may be known for their indistinct or muffled speech, causing them to be hard to understand. Other synonyms for mumbler include murmurer, low talker, and talking to oneself. A person who mumbles may also be described as a slurrer, stammerer, or muddled speaker. It is important to note that while someone may be labeled as a mumbler, it is crucial to approach communication with patience and understanding to ensure effective communication for both parties involved.