The AI-powered English dictionary
plural excursuses or excursus
A fuller treatment (in a separate section) of a particular part of the text of a book, especially a classic. examples
A narrative digression, especially to discuss a particular issue. quotations examples
Here is what us scholars call an excursus. If you are an honest man the following page or two can be of no possible interest to you.
1979, Kyril Bonfiglioli, After You with the Pistol, Penguin, published 2001, page 204
In his excursus on the Jewish people at the opening of the fifth book of his Histories [...], Tacitus was at a loss to uncover any deep cause for the war that broke out in 66.
2007, Glen Bowersock, “Provocateur”, in London Review of Books, 29:4, p. 16