Mustard Pee
The yellowish liquid that comes out from an upside down mustard bottle right before you squirt mustard onto a food item. Usually groans can be heard from the squirter indicating that mustard pee came out of the bottle instead of mustard.
Ugh! There's mustard pee all over my hot dog!
Mustard pee
Mustard pee- That undesirable yellow liquid that comes out first when you are really expecting mustatd and usually makes your sandwich soggy
I made a sandwich in the middle of the night. I wasn't awake and forgot to shake the mustard so all he got was mustard pee that made his sandwich all soggy.