regulator

noun9

1. •
   A device that controls or limits something.
2. •
   A person or group that sets standards of practice, especially regulatory law as sanctioned by statutory law.

   • […]in part because a key county reservoir had to been^([sic]) drained to reduce earthquake risks highlighted by federal regulators. — 2021
3. •
   A device that controls the supply of steam to the cylinders of a steam locomotive.

   • Driver G. A. Rowett, of the North Eastern Region's Neville Hill shed, now joined the locomotive as pilotman, and actually took over the regulator, Fireman Wheddon continuing to fire. — 1958
4. •
   Ellipsis of voltage regulator.

   • The regulator stopped working and the resulting overvoltage destroyed the device.
5. •
   Short for diving regulator.
6. •
   A gene involved in controlling the expression of one or more other genes.
7. •
   A very accurate clock, used by clockmakers to measure the timekeeping of each newly made clock.
8. •
   A positive real number determining the density of the units in Dirichlet's unit theorem.
9. •
   (historical) Synonym of bulldozer (“member of intimidating group of white US Southerners”).