Someone who's existence is merely a holding pattern in the toilet bowl of life and who will go swirling down the drain at the slightest decrease in forward inertia. So weak is their character and constitution, that the slightest emotional bump in the road will send them swirling away. They won't even have time to curl up in the fetal position and suck their thumb.
He's such swirlie. He quit his job, citing self-esteem issues, then spiraled further into depression and self-loathing after moving into his mother's basement.