Irony

Saying one thing while wanting another to be understood, often the opposite. The true meaning is left to the one who reads or listens.

In Madame Bovary

... whose mute ugliness has depths of expression, like the face of an imbecile

The narrator pretends to praise the cap when he says that its "mute ugliness" has "depths of expression," as if a meaningless object held something to say. The solemn praise is false: what he really says is that the object, and by extension its owner, is ridiculous.

Part I, Chapter 1, the narrator

Emma, in front of him, stared at him, did not share in his humiliation, but felt another: that of having imagined that such a man could have any worth, as if she had not already verified his mediocrity dozens of times.

Part II, Chapter 11, the narrator