object lesson
noun
ob·ject lesson ˈäb-jikt- 
-(ˌ)jekt-
: something that serves as a practical example of a principle or abstract idea
Example Sentences
His life story is an object lesson in how not to run a business.
Recent Examples on the Web That the greatest gun control victory in a generation might be the result of a legal technicality offers an object lesson about political mobilization. 
Jake Bittle, The New Republic, 9 June 2022 The vote-a-rama was thus, in itself, an object lesson of what was achievable in a 50-50 Senate. Grace Segers, The New Republic, 7 Aug. 2022 Working with a live audience and getting that instant feedback is an invaluable object lesson that has translated directly into writing good copy. Expert Panel®, Forbes, 19 May 2022 The scrappy salt box has become an unlikely icon, and an object lesson in the puzzling origins and even more puzzling manifestations of civic pride. Casey Cep, The New Yorker, 10 Apr. 2022 A few days after she was interviewed, Boichak’s Twitter feed provided an object lesson on the power of civilian stories to connect with faraway audiences. Washington Post, 8 Apr. 2022 The financial services giant, once presumed to be too big to fail, became a symbol — no, an object lesson — of Wall Street’s wanton recklessness. Los Angeles Times, 8 Mar. 2022 Mink farms threaten to become a source of new coronavirus variants — and an object lesson in how ‘spillback’ can make deadly diseases even deadlier. New York Times, 23 Jan. 2022 Though that initial panic may be overblown, Omicron is still extremely concerning — and an object lesson in the crazy risk of letting so much of Africa remain unvaccinated against COVID-19. Ryan Cooper, The Week, 30 Nov. 2021 See More
Jake Bittle, The New Republic, 9 June 2022 The vote-a-rama was thus, in itself, an object lesson of what was achievable in a 50-50 Senate. Grace Segers, The New Republic, 7 Aug. 2022 Working with a live audience and getting that instant feedback is an invaluable object lesson that has translated directly into writing good copy. Expert Panel®, Forbes, 19 May 2022 The scrappy salt box has become an unlikely icon, and an object lesson in the puzzling origins and even more puzzling manifestations of civic pride. Casey Cep, The New Yorker, 10 Apr. 2022 A few days after she was interviewed, Boichak’s Twitter feed provided an object lesson on the power of civilian stories to connect with faraway audiences. Washington Post, 8 Apr. 2022 The financial services giant, once presumed to be too big to fail, became a symbol — no, an object lesson — of Wall Street’s wanton recklessness. Los Angeles Times, 8 Mar. 2022 Mink farms threaten to become a source of new coronavirus variants — and an object lesson in how ‘spillback’ can make deadly diseases even deadlier. New York Times, 23 Jan. 2022 Though that initial panic may be overblown, Omicron is still extremely concerning — and an object lesson in the crazy risk of letting so much of Africa remain unvaccinated against COVID-19. Ryan Cooper, The Week, 30 Nov. 2021 See More Word History
First Known Use
1831, in the meaning defined above