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.

These words all mean to make something seem less wrong, evil, blameworthy, etc.

• Extenuate suggests the effort to lessen, or to decrease blame that has been incurred by an offense, while palliate implies concealment, to make less severe or intense, as of the incriminating facts or the gravity of their consequences.

To extenuate past neglect by present concern; to palliate the errors in a book:

"Starvation may serve to extenuate an instance of theft."
"A doting parent may seek to palliate the excesses of an errant son."
• Gloss over stresses the disguising or misrepresentation of incriminating facts; such as, to gloss over a mediocre academic record.
• To whitewash is to represent by completely false information or a dishonest judgment: "The accused man went free, whitewashed by a misguided board of investigation."