1. An extremely difficult, chaotic, or unpleasant day full of problems and stress
I had a hellish day at work with three meetings, two deadlines, and a broken computer.
Tive um dia infernal no trabalho com três reuniões, dois prazos e um computador quebrado.
2. A day characterized by unusually bad luck or misfortune
What a day from hell! Everything that could go wrong did go wrong.
Que dia infernal! Tudo que podia dar errado deu errado.