object lesson

WordReference Random House Learner's Dictionary of American English © 2026

ˈob•ject ˌles•son, n. [countable]

1. a practical or concrete demonstration or example of a principle:
   Watching him run that meeting was an object lesson in leadership.

WordReference Random House Unabridged Dictionary of American English © 2026

ob′ject les′son, 

1. a practical or concrete illustration of a principle.

• 1825–35

Collins Concise English Dictionary © HarperCollins Publishers::

object lesson noun

1. a convincing demonstration of some principle or ideal