Most disused refers to something that is rarely utilized or has fallen out of common usage. The antonyms for this term might include heavily used, popular, or frequently accessed. These words indicate that the item in question is valuable, in-demand, or actively utilized by a large number of people. Other potential antonyms could be essential, necessary, or required, which suggest that the item is critical to a particular function or purpose. Overall, the opposite of most disused suggests an item that is useful, influential, or integral to a specific task or objective.