To shut down is to close a business or switch off a machine completely. Shut down the factory, shut down the computer, the plant will shut down.
The down means fully and finally, which is why it is stronger than close. Of a person it means refusing to engage, and of an argument it means ending it flat.
1phraseshut downTo close a business or switch off a machine completely.
“Always shut down the machine properly rather than pulling the plug.”
shut down is a phrase.
Also accepted in games: close down
Practised in Phrasal Verbs