A quadriplegic is someone who has damage (and possible loss) of all four limbs on their body. It is usually caused by brain damage during an accident, where the limbs of the body become useless and need amputation. In a basic version, a quadriplegic is someone who has damage to both/loses both legs and arms during an accident and is just a body and head.
"Dude, did you see that quadriplegic? That shits fucking nasty!"