mustard shart 

The liquid that shoots out of a mustard container when you're expecting mustard, and not mustard juice/liquid.

This ruins a sandwich, even though you may have taken the percaution of squeezing it over the sink before your sandwich.

"damn, I made an awesome sandwich, but then I topped it off with mustard, and I got a nasty mustard shart instead!!"

mustard shart by chipoperson February 12, 2010

mustard shart 

When Tony eats an entire tub of mustard and subsequently shits his pants.

That Katz Deli Mustard Matt gave us was so good until I saw Tony mustard shart in his seat next to me.

mustard shart by Bigg Body October 3, 2018

Sharty Mustard Butt 

When somebody sharts in their underwear and wallows around in it for a long period of time. The color and texture resembles a mustard like substance.

Brian is a sharty mustard butt.

Sharty Mustard Butt by KrissyNJbo June 19, 2010