a tooth brush like device used exclusively to remove crust from one's grundle and can be used as a derrogatory insult towards someone
dude! i totally switched my grundle brush for this guy's toothbrush!

OR

senor badass is a grundle brush for not being creative
by meatyhandboy October 10, 2006
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Dude, don't trim your grundle brush 'cause you know I don't like it all prickly!
by D.S.B. November 27, 2016
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