The tangy yellow spread secreted from the anus during copulation - often used as a spread on chicken sandwiches.
Man, gimme some more of that butt mustard yo, my sandwich is dry.
by John November 12, 2003
The pasty by product of a long days work, and a bad wipe job after a long night of drinking beer and eating too many hotdogs.
Hey, look at the back of your pants, looks like you have a bit of Butt Mustard there.
by The Tatooed Nail Bender February 13, 2004
A fart that seeps out a little bit of liquid. Similar to a shart, but much less solid. Usually occurs after a heavy night of drinking.
When I farted, I thought it was okay, but then I felt the butt mustard squishing between my cheeks.
by stanleyroper July 02, 2005
The mix off blood, cum and shit that is often created during anal sex. It's dirty brownish yellow color and thick, soupy consistency resembles Dijon mustard.
How am I ever going to get that Butt Mustard off of my sheets before my girlfriend gets home?!?!?!
by Dan Lyons May 31, 2007
The watery sound ketchup/mustard makes when squeezed from a bottle.
Wow, Mike, that really sounded like a fart. No, dude, it was butt mustard. I was putting ketchup on my burger.
by Annie Farkle September 09, 2009