keyman

Noun

1. A telegraph operator.
   • Conscious of their importance, the 324 labor delegates marched bravely in and elected by acclaim as their president a onetime Ontario telegraph keyman, Senator Gideon Decker Robertson […] - 1932, Time (volume 19, part 2)
2. A workman who checks a railway track for faults, and who carries a keying hammer.
3. An employee of vital importance to a business.
   • A corporation may feel the need for life insurance on one of its keymen under a variety of circumstances. - 1957, Pearce Shepherd, Andrew C. Webster, Selection of risks:
   • As the keymen learn how to handle confidential company information, the owner-manager can disclose more to them. In most very small firms, the keymen will be "working" bosses. - 2000, Harvey C. Krentzman, The essentials...