unknownpart
nounUK /ʌnˈnəʊn pɑːt/
US /ʌnˈnoʊn pɑːrt/
A part that nobody knows about or has not found yet.
The robot had an unknownpart that made it stop working.
OTHER MEANINGS
2. A piece of a machine that is not named in the instructions.
The manual showed an unknownpart near the motor.
3. A secret or unclear section of a story or plan.
The last chapter was an unknownpart of the tale.
4. A spot on a map that has not been explored.
The explorers marked the island as an unknownpart.