master key

 Longman Dictionary of Contemporary English 5++朗文当代英语 5++LDOCE 5++朗文 5++ˈmaster key noun [countable]  DHHa key that will open all the door locks in a building 万能钥匙

Examples from the Corpus

master key• I went for help but the porter's master key also failed.• Safe in her own hallway, Miss Worthington bolted the front door, turned the master key.• The master key both advances the stage and records the total number of points counted.

ˈmaster key nounChineseSyllable  

door all that open Corpus the a key will

master key
ˈmaster key noun [countable]
a key that will open all the door locks in a building

master keyBrE /ˈmɑːstə kiː/ 🔊NAmE /ˈmæstər kiː/ 🔊 (also ˈpass key) nouna key that can be used to open many different locks in a building 万能钥匙