Top definition
A mustard that is under the arm in the pit.

Armpit mustard became popular when Ethan Dolan spoke on twitter about having this condition.
Grayson: Yo bro!
Ethan: Yeah bro?
Grayson: What’s that pastey stuff under your arm man?
Ethan: Oh that? That’s just my armpit mustard man
Grayson: Cool dude!
Ethan: Yeah man
by anon1027 February 21, 2018
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2
Armpit mustard is when you have an armpit and you put mustard on it . Quote : The Dolan Twins.
Girl 1: Do you like Ethan’s armpit mustard ?
Girl 2: Of course I do , don’t you?
by Ranraccoon324 April 23, 2018
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