master key

American

noun

a key that will open a number of different locks, the proper keys of which are not interchangeable.

master key British

noun

Also called: pass key. a key that opens all the locks of a set, the individual keys of which are not interchangeable

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Etymology

Origin of master key

First recorded in 1570–80

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

Professor Jonathan Heeney of Cambridge University likened the new technique to having the "master key" for an apartment block.

From Barron's • Jun. 25, 2026

Antibodies can sometimes act like a master key, helping trigger immune responses.

From Science Daily • Jan. 9, 2026

Apple told the BBC in a statement that it had "never built a backdoor or master key to any of our products, and we never will".

From BBC • Feb. 26, 2025

Mitchell also went into Blanchard’s chambers in 2023 by using a master key, the commission wrote.

From Los Angeles Times • Feb. 13, 2025

“They must have some way to let people in. Do they have a master key in the office?”

From "Tangerine" by Edward Bloor

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023