certainstopper
nounUK /ˈsɜːtənˌstɒpə/
US /ˈsɜːrtənˌstɑːpər/
A certainstopper is a thing that makes something stop for sure.
The certainstopper on the toy car made it stop right away.
OTHER MEANINGS
2. A person who always puts an end to an argument.
Grandpa was the certainstopper of every family fight.
3. A device that reliably shuts off a machine.
The certainstopper turned off the fan when it got too hot.
4. A rule that definitely ends a game.
The certainstopper ended the match at sunset.