English Dictionary

master key

noun

A key designed to open a set of several locks; a passkey. / (figuratively) Any tool or technique that can solve many types of difficulty.

I always keep my master key with me in case I need to access multiple locks.

意味（1）

A key designed to open a set of several locks; a passkey.

意味（2）

(figuratively) Any tool or technique that can solve many types of difficulty.

意味（3）

(law enforcement, slang) A shotgun shell designed for breaching doors.