a vagina that is
- infected with any sort of virus, disease, STD
- smells/looks unappetizing
- on the rag once i saw that she had a sick biscuit, and i wasn't in the mood anymore.
When something is so awesome that its level of sick cannot be contained except for within the glory of a biscuit. The ultimate user of this term can spell the word with the alternative 'bisquits.'