Q: What is a good aphantasia definition? A: Aphantasia can best be defined as the inability to create voluntary mental images. So when one who experiences aphantasia thinks of a black cat, they would not get any sort of sense of what a black cat looks like. However they may experience a list of descriptors in their mind, as if they're repeating details about a black cat back to themselves (eg: black, cat, furry, slender, etc... ).