A Geoffrey is a marijuana joint laced with many other drugs such as Heroin, LSD, Cocaine, and methamphetamines. In the movie, "Get Him to the Greek" Aaron Green (Jonah Hill) smokes a Geoffery with Aldous Snow (Russell Brand) and his father in Las Vegas causing him to have a heart attack thus provoking Aldous to stab Aaron in the heart with an Adrenaline shot, overiding the heart attack. Smoking a Geoffery also makes the person very attracted to furry walls.
Aaron: What is this?
Aldous: It's a Geoffrey
Aaron: What the hell is a Geoffrey?
Aldous's Father: It's a joint laced with Heroin, LSD, cocaine, extacy, and I think it has PCP.
Aaron: Why do they call it Geoffrey?
Aldous's father: Because who is going to be scared of a bloke named Geoffrey?
Aaron: Ahh God, I'm having a heart attack