1. A subjunctive phrase expressing a wish, command, or hope that someone remains awake or conscious
I hope that you stay awake during the entire presentation.
Espero que você fique acordado durante toda a apresentação.
2. Used to warn someone not to fall asleep or lose consciousness in a critical situation
Stay awake! We need to keep you conscious until the ambulance arrives.
Fique acordado! Precisamos mantê-lo acordado até a ambulância chegar.