1. A short definition, explanation, or translation of a word or phrase that may be unfamiliar to the reader, often located in a margin or collected in an appendix or glossary of a book.
2. A brief explanatory note or translation of a difficult or technical expression which is usually inserted in the margin or between lines of a text or manuscript or a collection of such notes.
3. An extensive commentary, often accompanying a text or publication.
4. A purposefully misleading interpretation or explanation; to give a false interpretation to something.