one who 'tweaks balls' as in one who uses the drug methamphetamine to get amped and then shakes around and talks non-stop.
I would have asked Mary to help me study for my test but she's such a tweaker --she couldn't sit still for more than 2 minutes so that's why I got a D+
Someone using Crystal meth or ice are referred to as tweakers. They are commonly referred to as tweaking out as in a state of paranoia or moving and twitching profusely.