Definition of key man in US English:

key man

noun

  • 1A man who plays a leading or important role in a group, an industry, etc.

  • 2Chiefly US. A telegraph operator. Now historical.

Origin

Late 19th century; earliest use found in Congregationalist. Probably partly from key + man, and partly from key + man.

Pronunciation

key man

/ˈkiː man/