When a foot fungus goes unchecked and starts secreting a strange yellow substance. That substance is called foot mustard.
Dude, get a doctor to check out your foot mustard situation, it's seriously gross.
by Aria Stormshine April 11, 2016
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To have smelly feet or some funky shit growing on your foot.
Damn, did you smell her feet in the car? Yea, that's some straight-up Mustard Foot dawg.
by Nagnal August 16, 2019
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