The term 'nude rat' is not a word with any sense of meaning under the English language. Therefore, it wouldn't have antonyms that are directly connected to the term. However, if the two words are considered to be separate, the term 'nude' refers to a state of being unclothed, while 'rat' refers to a small furry animal with a long tail. Possible antonyms for 'nude' could be clothed, adorned, or decorated. On the other hand, antonyms for 'rat' could be clean, pure, hygienic, and immaculate. But, again, as there is no usage or sense of meaning to the term 'nude rat' as a whole, the search for antonyms for it is invalid.