Sparkliness is defined as the quality of being glittery or shiny. When looking for antonyms, we can find words that describe the opposite of these characteristics. Some excellent examples are dullness, plainness, and flatness. If something is not shiny or does not sparkle, it is plain and dull. For instance, dullness can describe an object that is dirty, lackluster, or without shine. Furthermore, flatness can describe a surface or object that is uniform, smooth without any textures or ruggedness. In summary, the antonyms for sparkliness are dullness, flatness, and plainness, which are all used to define an object or surface that lacks shine or glitteriness.