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1. To begin functioning or operating after connecting to a power source. He began reading the memos for the day while waiting for the computer to power up.
2. To activate something, especially a computer or computer system, especially by connecting or prompting it to connect to a power source. In this usage, a noun or pronoun can be used between "power" and "up." I always sit down at my desk and have a cup of coffee before I power up my computer and start work for the day. OK, power the engines up and steer the plane onto the runway.
power something up
to start something, such as an engine. You should power the engine up and let it run awhile before you drive away. Power up the engine and mow the grass.
to start an engine. Well, let's power up so we will be ready to leave with the others. It's time to power up and get going.
1. To activate some device and prepare it for operation: The pilot powered up the engines and prepared to take off. I replaced the memory chip and powered the computer up and to see if it worked.
2. To start operating and become ready for use: Wait a few seconds for the computer to power up.