extrakey
nounUK /ˈɛkstrəkiː/
US /ˈɛkstrəkiː/
A key that you keep just in case you need one more.
She hid an extrakey under the flowerpot for her sister.
OTHER MEANINGS
2. An additional button on a keyboard or keypad.
The extrakey on the remote opens the settings menu.
3. A bonus answer or hint in a puzzle or game.
Solving the riddle gave him an extrakey to the next level.
4. A second musical key used in a piece or performance.
The song shifts to an extrakey during the chorus.