The clear liquid that dribbles out before the mustard when you squeeze the bottle. This usually happens when the mustard sits for a long period of time.
Gross, I just got mustard pre-cum on my sandwich.
by Jeff the bear March 10, 2010
That watery shit that comes out before you squirt your mustard
I just shot so much mustard precum. It's gonna ruin my weiner
by Joeyfromtheblock March 11, 2015