slave driver

WordReference Random House Learner's Dictionary of American English © 2025

ˈslave ˌdriv•er, n. [countable]

1. an overseer of slaves.
2. a demanding leader or boss.

WordReference Random House Unabridged Dictionary of American English © 2025

slave′ driv′er, 

1. an overseer of slaves.
2. a hard taskmaster:
   His boss was a slave driver.
• 1800–10, American.

Collins Concise English Dictionary © HarperCollins Publishers::

slave-driver noun

1. (esp formerly) a person forcing slaves to work
2. an employer who demands excessively hard work from his or her employees