The word "most mumpish" can be described as someone who is sulky, disgruntled, or moody. Antonyms for "most mumpish" include traits like cheerful, content, and happy-go-lucky. You could also describe someone who is "most mumpish" as being uncooperative or difficult, so antonyms may include cooperative, amenable, or flexible. Additionally, someone who is "most mumpish" may be easily frustrated or annoyed, so antonyms may include patient, tolerant, or understanding. It's important to note that antonyms for "most mumpish" may vary based on the context in which the word is being used.