object lesson

American  

noun

1. a practical or concrete illustration of a principle.

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object lesson British  

noun

1. a convincing demonstration of some principle or ideal

2. (esp formerly) a lesson in which a material object forms the basis of the teaching and is available to be inspected

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Etymology

Origin of object lesson

First recorded in 1825–35

Example Sentences

In the Middle Ages, the French disaster at Crécy became an object lesson in the dangers of rushing in.

From Slate • Apr. 13, 2026

Industry insiders have told the BBC that Fishwick is now regarded as an object lesson in how not to run an installation project.

From BBC • Oct. 30, 2025

That’s the bigger story that is being lost in the government’s egregious, ham-handed attempt to turn Ábrego García into an object lesson.

From Salon • Jul. 17, 2025

Put it all together, and the Boeing story looks like an object lesson in what happens when management takes its eye off the ball — or more precisely, puts it eye on the wrong ball.

From Los Angeles Times • Sep. 10, 2024

He was a walking object lesson about how dangerous work in the Fishery could be.

From "The Name of the Wind" by Patrick Rothfuss