There are several synonyms for the word "butt", which is commonly used to refer to a person's behind. Some of the most common synonyms include "derriere", "posterior", "backside", "rear-end", and "bum". Other more colloquial synonyms include "booty", "tush", "buttcheeks", "glutes", and "heinie". In some cultures, the word "keister" is also used as a synonym for "butt". Regardless of the word used, it is essential to be mindful of the context and audience when selecting synonyms for this particular body part.