OH YEAH! Share definition Flag The slogan of the kool aid man, used jokingly by people after another person says 'Oh No' or something very serious. Judge: I sentence you to 24 months in prison Lois: Oh no. Meg: Oh no. Brian: Oh no. Kool Aid Man: OH YEAH! OH YEAH! by Banksie July 3, 2006 Get the OH YEAH! mug.