"Flapping" is a colloquial term that often refers to a behavior sometimes exhibited by individuals with autism spectrum disorder (ASD).
It involves repetitive and rhythmic movements of the hands, fingers, or other body parts. This self-stimulatory behavior, or "stim," can help individuals with ASD self-regulate and manage sensory overstimulation or stress. While flapping is a common stim behavior, it's essential to recognize that stimming is a natural coping mechanism for some individuals on the autism spectrum, aiding them in processing their environment and emotions.