1to close; to shut (a window etc)
2(of a shop, school etc) to shut down
Examples
shǒu xiān首先，guān bì关闭shǒu jī手机，bǎo chí保持ān jìng安静。
首先，关闭手机，保持安静。
First of all, power off your cellphones and remain silent.
关闭所有的门和窗户。
Shut all the doors and windows.
请关闭你的手机。
Please turn off your cellphone.