a large, cheesy grin on a person, similar to the one the Kool-Aid man has in the commercial. A Kool-Aid Smile is usually seen when a person has accomplished a major feat or task, or something extraordinarily good happens to that person.
by Rey Del Fuego November 11, 2007
When a guy goes down on a girl who is on the rag and when he comes up he has a ring of period blood around his mouth that resembles the effects of drinking red Kool-Aid.
So I went down on her last night, and she was on the rag, when I came up I had the biggest Kool Aid Smile ever.
by Anonymous_Hero April 04, 2010