shoulder-biter

Slang term for someone with learning difficulties or a mental disability. Alternatively, someone who is acting like a moron. Origin stems from random, sporadic open-mouthed head movements typical of sufferers where they appear to be trying to bite their own shoulder.

'Shoulder Biter' (Shoulder biting)
An action usually undertaken by a wheelchair bound retard. Because they cant keep their necks straight or mouths closed, they usually wheel about literally biting their own shoulder(s) ..