from The American Heritage® Dictionary of the English Language, 4th Edition
- n. Slang A deranged, psychotic, or morbidly obsessed person.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A day taken off work due to (possibly exaggerated or supposed) illness.
- n. A person with unpleasant tastes, views or habits.
- n. A mentally ill person.
From sick1.(American Heritage® Dictionary of the English Language, Fourth Edition)
sick + -o (Wiktionary)