drunk sex is when the people having sex and they are drunk and have absolutley no idea what they are doing. Also, they don't remember what happened when they wake up or when the finally become sober. It is also the best type of sex, most people say.
guy: Babe, i didnt know...i was drunk
girl: why did you have to go have drunk sex with some slut? We could've just had memorable sex with eachother? :(