Some children with autism “hand flap” as a self-stimulatory behavior. Other self-stimulatory behaviors sometimes seen in children with autism include rocking and spinning. These behaviors help them calm themselves or regulate their emotional states. Children may also do it when excited or upset, and it can be very hard to distract an autistic child away from their self-stimulatory behavior.
by SamDeHam March 15, 2017
When you are about to go down on a girl and you start flapping her vagina lips with your hands. Hence, a HAND flap.
Boy: "Are you ready for this babygirl?"
Girl: "What.. WHAT ARE YOU DOING?"
Boy: "I'm hand flapping you babe."
Girl: "What.. WHAT ARE YOU DOING?"
Boy: "I'm hand flapping you babe."
by Maaashaa February 9, 2015