The word top-most represents the highest position on something. Its antonyms can be used to denote the opposite or lowest position. The antonyms for top-most can be bottom, baseline, underneath, lowest, or base. They are used to represent the lowest level of something or the foundation. For instance, in visual arts, the bottom layer is the baseline or the bottom-most layer. When it comes to architecture, the foundation of the building represents the lowest point, also known as the base. In the end, the antonyms for top-most play a vital role in differentiating between the highest and the lowest position of things.