to spaz, spazzing.
"My leg/arm/head/otherbodypart's spazzing" - which is when aforementioned body part twitches erratically.
"She's totally spazzing." - when somebody is going mad ^^
Also can apply to people who are nervous, jumpy, hyper and needs to take medication to calm down. Uusally a spazz will blurt out unneccasary things to get attention.