mustard booger Posted in M Best definition mustard booger (n) the little crusty bit of mustard that forms at the nozzle of a squeezable mustard container Before squeezing mustard all over my hot weiner, I picked off the mustard booger. How satisfied are you with the definition? Looking for mustard booger meaning? Delighted that you discovered the greatest determine on our web site! Recently this definition was actually observed 45 times.