A fork of Rural Dictionary
1. A term for a woman's vagina, when receiving cunnilingus, has a sharp, sour, foul taste reminiscent to that of the condiment mustard.
2. A term for a woman's vagina that gives off such a foul odor so strong that it could result in casualties, much like Mustard Gas.
"Damn, girl. You need to do something about that mustard biscuit you got between your legs."
This is a phrase used to trick a gullible person who feels the need to define every new word they happen to hear or read into searching for this and thus, being "sacrificed" to the saints.
The "saints" this refers to are two saints: St. Fiacre, who is the patron saint of venereal disease (most things people have the insatiable desire to define are sexual) and St. Isidore of Seville, who is widely considered the patron saint of the internet.
"That guy always has to go to UrbanDictionary.com to find the definition to everything so I told him I did a 'sacrificing to the saints' with my girlfriend. That'll teach him to believe everything he hears."