offswitch
nounUK /ˈɒf.swɪtʃ/
US /ˈɔːf.swɪtʃ/
A button or lever you press to make something stop working.
Press the offswitch to turn off the lamp.
OTHER MEANINGS
2. A way to stop or end something quickly.
The manager used the offswitch on the project when it got too expensive.
3. A feature that lets you hide or disable something online.
She flipped the offswitch on notifications so her phone stayed quiet.
4. A person or thing that suddenly ends a good mood or activity.
His grumpy comment was the offswitch for the whole party.