Bolted down typically refers to securing an object or piece of furniture in place. Antonyms for bolted down would be unfastened, loose or unsecured. Unfastened means not locked or secured. Loose means not tight or fixed firmly in place. Unsecured means not protected against damage or theft. Therefore, if an object is unfastened, loose or unsecured, it can easily move or be stolen, resulting in potential danger or loss. It is always important to make sure that an object is bolted down properly before leaving it unattended to avoid any unwanted mishaps.