Machadiano is the adjective for what recalls Machado de Assis's way of writing: a narrator who comments on his own narrative, talks with the reader, uses irony, and is less interested in action than in what moves people beneath good manners.
The Posthumous Memoirs of Brás Cubas shows these traits well. Right in the prologue, the narrator warns: "if you do not like it, I will pay you back with a flick of the finger, and goodbye." In the first chapter, he says that he is "not an author who is dead, but a dead one who authors." The narrator interrupts the plot, goes back, corrects what he has said, and treats the reader as an interlocutor.
Scholars describe this procedure as irony in the literary sense: the narrator distances himself from what he tells, questions facts and characters, and may ridicule even the character he himself once was. The critic Roberto Schwarz argues that Machado's narrative innovations expose the hypocrisy and the malfunctioning of nineteenth-century Brazil.
There is one caveat: some critics list general characteristics of the style without checking whether they hold for every work, so that machadiano describes a tendency, not a rule applied equally to each book.
On Clavis: The Posthumous Memoirs of Brás Cubas.