Debauchery is a noun meaning crazy partying and wild nights, usually accompanied by a lot of alcohol. So you probably don't want to engage in any kind of debauchery the night before an exam.
Debauchery is all about indulging in some of life's pleasures — overindulging, in fact. It stems from the Middle French word debaucher, which means to “entice from work or duty.” So imagine workers being tempted from another day at the office by the promise of a wild bender in Vegas. Or college kids putting down the books and heeding the siren call of the frat party downstairs.