What it means:

n. (gas' tro en' te ri' tis)- Inflamation of the stomach and intestines.

What makes it cool:

If you ever sleep through a test or forget to turn in an assignment and you're not sick, go to the University Health Center (or its equivalent in your location) and tell them you have 1 or more of the following symptoms: fatigue, chills, loss of appitite, nausea, vomiting, stomach cramps, diarrhea, low-grade fever. Then they will tell you that you have gastroenteritis, which is serious enough to excuse a missed test, or a late assignment, but not serious enough for medication or a visit to a real doctor. Furthermore, gastroenteritis is code in the UT system for, "I missed a test, but I know the secret code to make it up." It works a lot like the Illuminati or the Freemasons; all you have to do is know the secret word, and you're in! So that's why this is the Exhilerating Cool Word of the Month - Gastroenteritis.