master key 
noun
A key that opens several locks, each of which also has its own key: the master key for all the safes in the department...
- The change key will open only that specific lock, while the master key will open that lock and several others in a group.
- She used her master key to open the lock, and began to open the gate.
- I got the master key and opened the door and that's when I saw him in the bath.
- neurocentral
- neurochemical
- neurochemically
- neurochemist
- neurochemistry
- neurochord
- neurocirculatory
- neurocirculatory asthenia
- neurocoel
- neurocoele
- neurocognitive
- neurocomputer
- neurocomputing
- neurocranial
- neurocranium
- neurocrine
- neurocutaneous
- neurocyte
- neurocytologic
- neurocytological
- neurocytologist
- neurocytology
- neurocytoma
- neurodegeneration
- neurodegenerative