Commonly used to describe a situation in which a person spends a long period of time forgoing sleep and sometimes other necessities to prepare for something. Hell Week gets its origins from the Fifth week of the First Phase of BUD/S (for those of you who don't know what it is, it is the training course that Navy SEALs go through) where for five days, they are subjected to living hell where with no sleep, they are required to perform strenuous physical activity in combat conditions at Olympic standards.
1. Before Hell week, there were 102 SEAL candidates, but afterwards, there were only 50.
2. Before the enormous final, an academic hell week began. There was non-stop studying, there seemed to be an unwritten law against sleep, and the neighborhood Starbucks made incredible amounts of money.