| 1. | an object or device that shuts (something) off: the automatic shutoff on a heater. |
| 2. | an act or instance of shutting off something, as an opening, a flow, or a service: a shutoff of electric power due to unpaid bills. |

verb, shut, shut⋅ting, adjective, noun | 1. | to put (a door, cover, etc.) in position to close or obstruct. |
| 2. | to close the doors of (often fol. by up): to shut up a shop for the night. |
| 3. | to close (something) by bringing together or folding its parts: Shut your book. Shut the window! |
| 4. | to confine; enclose: to shut a bird into a cage. |
| 5. | to bar; exclude: They shut him from their circle. |
| 6. | to cause (a business, factory, store, etc.) to end or suspend operations: He shut his store, sold his house, and moved away. We're shutting the office for two weeks in June. |
| 7. | to bolt; bar. |
| 8. | to become shut or closed; close. |
| 11. | the act or time of shutting or closing. |
| 12. | the line where two pieces of welded metal are united. |
| 13. | shut down,
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| 14. | shut in,
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| 15. | shut of, Informal. free of; rid of: He wished he were shut of all his debts. |
| 16. | shut off,
|
| 17. | shut out,
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| 18. | shut up,
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shut off
Stop the flow or passage of, as in They shut off the water while repairs were being made. [Early 1800s]
Close off, isolate, as in Loners shut themselves off from the community. [First half of 1800s]