object lesson

American

noun

a practical or concrete illustration of a principle.

object lesson British

noun

a convincing demonstration of some principle or ideal
(esp formerly) a lesson in which a material object forms the basis of the teaching and is available to be inspected

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Etymology

Origin of object lesson

First recorded in 1825–35

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

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

From Slate • Apr. 13, 2026

He and his representatives are now threatening Cuba, Mexico, Colombia, Iran and Greenland, with Venezuela serving as an object lesson of what may happen if a country dares to disobey his wishes.

From Salon • Jan. 6, 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

He gave a television interview that was so legendarily awful it’s become an object lesson in how not to start a campaign.

From Los Angeles Times • May 18, 2025

Cicero, then, offers an object lesson for orators in the importance of watching your mouth.

From "Words Like Loaded Pistols" by Sam Leith

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023