Stim is short for stimulating. It's a repetitive movement that people with ASD do to calm down. This can be rocking back and forth, blowing on fingers, playing with hair, walking back and forth, waving hands, spinning objects, clicking their tongue, etc. Most people stim a little bit but people with ASD do it in a way that's far more obvious. I've been a childcare worker for children with ASD for 5 years.

Also, having asperger's syndrome is nothing to be ashamed of. The guy who invented Pokemon and Bill Gates both had it and look how successful and loved they are!