yooy Share definition Flag is an adj. used to express an epic grammatical mistake or pronunciation. "Huss:he wannas die !!! Janko: wtf do you mean ? there's no such thing . you're such a yooy." yooy by definer guro January 26, 2016 0 0 Get merch Get the yooy mug. Buy Now — $32.95 See more merch