Definition of "decorum"

It was sort of a finishing school. You know, to teach proper social decorum and so on and so forth.

2010, Pseudonymous Bosch (pseudonym; Raphael Simon), This Isn't What It Looks Like, ch. 4

Mr. Trump’s volcanic performance appeared to be the gambit of a president seeking to tarnish his opponent by any means available, unbounded by norms of accuracy and decorum and unguided by a calculated sense of how to sway the electorate or assuage voters’ reservations about his leadership.

2020 September 29, Jonathan Martin, Alexander Burns, “With Cross Talk, Lies and Mockery, Trump Tramples Decorum in Debate With Biden”, in New York Times‎

Democrats in the House chamber burst into raucous laughter when Marjorie Taylor Greene called for “decorum”.

2023 May 25, Martin Pengelly, “House Democrats laugh off Marjorie Taylor Greene’s call for ‘decorum’”, in The Guardian‎

In the architecture and embellishments of the chamber, the evident design was to dazzle and astound. Little attention had been paid to the decora of what is technically called “keeping,” or to the proprieties of nationality. The eye wandered from object to object, and rested upon none; neither the “Grotesques” of the Greek painters, nor the sculptures of the best Italian days, nor the huge carvings of untutored Egypt.

1834 January, [Edgar Allan Poe], “The Visionary”, in The Lady’s Book, page 41, column 2