Noun. gathering where both male and female participants engage in a variety of sexual and monoganous activity. The ultimate slug fest is when anuses are involved and a minimum of double penetration is generally required.
"Jim, Jim's friends, jane, and jane's friends engaging in group sex while influenced by alcohol."
"They'll be lot's of spreading out our slug fest, should I sign you up for one hole or two?"
"Would you like to partake in our slug fest?"