(n) a disease caught by those who attend Gunn High School, Palo Alto, and some surrounding schools. Symptoms generally start to appear junior year, though they may be present as early as sixth grade in some cases. Short-term effects include mad AP classes as well as extracurriculars, caffeine addiction, intense sleep-deprivation, a triple-booked schedule, no time for family and/or friends, and chronic talking online at 5AM while doing homework.
Long-term effects include acceptance to Stanford(in severe cases), heart disease, and a "BRING IT ON" mentality regarding life that will haunt you to your grave.
I was studying AP Biology while on a volunteer worksite in Canada over spring break and talking in French to my professor online, when I realized what a totally *Gunnitis* moment it was.