The word "more estival" refers to something that is summery or related to summer. The antonyms for this word would be anything that is winter-related or cold. Some examples of antonyms for "more estival" include wintry, frigid, chilly, autumnal, and cool. The opposite of summery would be something that is related to the colder months, such as snow or frost. When you think of summer, you think of bright sunshine, warm temperatures, and beach days, but when you think of winter, you think of ice, snow, and the holidays. Thus, the antonyms for "more estival" would take on a completely different vibe than the original word.