The word medium-sized is often used to describe something that is not too big or small. However, it is important to have a variety of vocabulary to describe objects or entities, and antonyms for "medium-sized" can be helpful in achieving this. Some possible antonyms for medium-sized include 'tiny,' 'small,' 'minuscule,' 'big,' 'large,' 'tremendous,' 'enormous,' or 'gigantic.' While using precise language may not be essential in general conversation or everyday writing, it becomes critical in specialized contexts such as scientific or technical writing, where an author may need to distinguish between different size categories.