lonekey
nounUK /ˈləʊnkiː/
US /ˈloʊnkiː/
A lonekey is a special key that works all by itself.
She found a lonekey hidden under the doormat and used it to open the old shed.
OTHER MEANINGS
2. A key that is the only one of its kind, with no copies made.
The museum keeps a lonekey for the rare cabinet so no one can duplicate it.
3. A password or code that grants access on its own, without any other step.
The app sends a lonekey to your phone so you can log in with just one tap.
4. In a game, a special key that appears alone and opens a secret door.
Grab the lonekey on level three to unlock the treasure room.