The term 'KIND OF ILLUSION' can be solved by the crossword solution 'OPTICAL' (7 letters). An OPTICAL illusion is a type of illusion that is caused by the visual system and characterized by visually perceived images that differ from objective reality. OPTICAL illusions are often characterized by visually perceived images that are different from the object's true properties. They can be caused by a variety of factors, including the way in which the eye perceives light and color, the way in which the brain processes information, and the way in which the environment affects the perception of an object.