The word "un-tidiest" implies that something is messy, disorganized, or in a state of chaos. To express the opposite meaning, we can use antonyms such as "neat," "tidy," "well-organized," "orderly," or "systematic." These words describe a situation where everything is arranged in a proper manner, and there is a sense of cleanliness and discipline. Antonyms of "un-tidiest" also include words like "meticulous," "methodical," "fastidious," and "precise," which suggest a high level of attention to detail and an emphasis on maintaining order. It is important to understand antonyms to improve our vocabulary and use the right word to convey the intended meaning.