If a machine or system shuts off, or if someone or something shuts it off, it stops operating.

The engine shuts off automatically when the desired speed is reached. 达到设定的速度后，发动机会自动关闭。

to stop the supply of something

Did you remember to shut off the water and gas before you left the house? 离开房子的时候，你记得关掉水和煤气了吗?

Oil supplies have been shut off. 燃油供应被切断了。

to prevent something from being reached or seen

The music room is shut off from the rest of the house by a soundproof wall. 隔音板把音乐间和屋内的其他房间隔开了。

A row of tall fir trees shuts off the view of the street in front. 一排高大的杉树挡住了前面的街景。

to stop speaking to other people or stop being involved with them

When her husband died she seemed to shut herself off from her friends and family. 丈夫去世后，她似乎不再与她的朋友和家人来往了。