The mixture of ejaculate and grey matter that is churned as the result of skull fucking.
As Jess got up to go freshen up, an amount of brain butter leaked out of her eye socket. Brian caught it and was able to spread it on an english muffin which he enjoyed on his commute to the office.
by brainbutter February 16, 2010
A girl that has a nice body and a beautiful face but she's dumb as shit.
Lauren is so fucking hot but she is a huge butter brain.
by Lakitaari January 18, 2011