STD
n. A pejorative nickname for the Sigma Delta Tau sorority, due to the fact that a reasonable number of its members have a reputation for sleeping around. Alternatively, some people also call it "EAT," because of how the Greek letters look. Is it true? Ask around campus!
Female Student: So, I'm pledging for Sigma Delta Tau for rush this week!

Friend: You're pledging for STD? Don't contract one!