Infodump
A block of exposition interrupting the story to explain the world, its history or technology — speculative fiction's enemy #1.
An infodump is a passage where the author suspends the fiction to explain directly: three pages of the kingdom's history, the star drive's workings, the noble houses' genealogy. Its dialogue variant, the "As you know, Bob," has two characters explain to each other what both already know.
The problem isn't information but form: lectured at, the reader shifts from witness to student, and emotional memory disengages. The proven alternatives: reveal through action and conflict, filter through a character to whom the information costs or matters, release in fragments, and exile the encyclopedia to appendices — like Dune's glossary.
Example
"As you know, brother, our father died seven years ago at the Battle of Ashes…"