Someone who surfs the web too much, so much in fact, that they have devolved into a pale gelatinous blob who can no longer lift themselves out of their chair. The cyber larva will have to eat by means of robotic feeding tube, and excrete by means of auto-cleaning bed pan or colostomy bag. The cyber larva's limbs will eventually diminish into nubbins, except for a very pronounced mouse clicking tentacle.
Eric used to be top of his class. He was also president of the chess club, volunteered down at the homeless shelter, and was top runner on the cross country team. The he became addicted to the internet. You wouldn't recognize him. He's become a cyber larva.