As I recall, this was more of a joke than an actual grade. I'd have to re-read to see if I am remembering correctly.Skintigh 23:30, April 2, 2010 (UTC)

It is confirmed at JKR's Official Site to be an official Wizarding Examinations Authority grade (see the image on the article). --  Seth Cooper  owl post! 23:44, April 2, 2010 (UTC)
It's also visible in Half Blood Prince under the "fail grades" on Harry's O.W.L. results. --Cubs Fan (Talk to me) 00:04, April 3, 2010 (UTC)
Plus it's a grade you can achieve (if that's the right word) in the OotP video game (although that is not considered canon). Christophee (talk) 00:18, April 3, 2010 (UTC)
Actually, video games are considered canon as long as they are not contradicting anything. Just wanted to make that clear.--L.V.K.T.V.J.Hogwarts(Send an owl!) 00:50, April 3, 2010 (UTC)