1. To turn off or shut down a device, system, or machine by cutting off its power supply
Please power down your computer before leaving the office.
Por favor, desligue seu computador antes de sair do escritório.
2. To reduce power or energy output gradually
The reactor began to power down safely after the emergency shutdown was initiated.
O reator começou a reduzir gradualmente sua potência após o desligamento de emergência.
3. To lose energy or momentum; to become less active or alert
After a long day of work, I just want to power down and relax.
Após um longo dia de trabalho, só quero desligar e relaxar.