1. A disturbing or frightening dream that occurs during sleep, typically causing distress upon waking
I had a terrible nightmare last night about falling from a building.
Tive um pesadelo terrível na noite passada sobre cair de um edifício.
2. A situation or experience that is extremely unpleasant, stressful, or difficult to endure
Organizing that event was an absolute nightmare.
Organizar esse evento foi um verdadeiro pesadelo.