1. A key that opens many locks or resolves many difficulties.

Nuttall's Standard dictionary of the English language By Nuttall, P.Austin

• masterkey,
• naster key,
• kaster key,
• jaster key,
• mzster key,
• msster key,
• mwster key,
• mqster key,
• maater key,
• mazter key,
• maxter key,
• madter key,
• maeter key,
• mawter key,
• masrer key,
• masfer key,
• masger key,
• masyer key,
• mas6er key,
• mas5er key

The adjective form of the word "master key" is "master-keyed".

The plural of the "master key" can be the "master keys".

The singular of the "master key" can be the "master key".