Chiasmatic is an uncommonly used word that describes something that is related to the optic chiasm, which is the point where the optic nerves cross over each other inside the brain. Some synonyms for chiasmatic include decussate, intersecting, intertwining, and crisscrossing. These words depict the crossing or overlapping of two different things. Another synonym for chiasmatic is "X-shaped", which is how the optic nerve fibers appear when they cross over. These words can be used to describe a variety of things, including nerve pathways, patterns, and even behaviors, as long as they involve the crossing of two different elements in an X shape.