Closed-down refers to something that has ceased operations or stopped functioning. Its antonyms, on the other hand, would mean the opposite or the reversal of the word's meaning. Some common antonyms for closed-down are active, operational, functioning, open, and operating. When a business is open, it means that it is in operation and is accepting customers or clients. The opposite of a closed-down restaurant is an operating restaurant, where diners can enjoy delicious meals. Similarly, an open shop is a place where people can shop for groceries, clothes, and other essential items. In short, the antonyms of closed-down are terms that signify the existence and continuation of various activities and operations.