mysterybutton
nounUK /ˈmɪstəriˌbʌtən/
US /ˈmɪstəriˌbʌtən/
A mystery button is a button that does something surprising when you press it.
She pressed the mystery button and a funny sound came out.
OTHER MEANINGS
2. A button whose purpose is kept secret on purpose.
The game had a mystery button that opened a hidden door.
3. A button in a story or game that gives a random result.
Every time he tapped the mystery button, he got a different prize.
4. A button that looks ordinary but is not explained.
The old machine had one mystery button nobody dared to touch.