The buttocks (singular: buttock) are rounded portions of the anatomy located on the posterior of the pelvic region of the apes, including humans and many other bipeds or quadrupeds.

Anatomy

The buttocks allow primates to sit upright without needing to rest their weight on their feet as four-legged animals do. Females of certain species of baboon have red buttocks that blush to attract males. In the case of humans, females tend to have wider and thicker buttocks due to higher subcutaneous fat and wider hips.

Some baboons and all gibbons, though otherwise fur-covered, have characteristic naked callosities on their buttocks. While human children generally have smooth buttocks, mature males and females have varying degrees of hair growth, as on other parts of their body. Females generally have hair growth in the gluteal cleft (particularly around the anus), often extending laterally onto the lower aspect of the cheeks. In addition to such areas, males often have hair growth over the most (or the entirety of) the buttocks.

Connotations

The English word of Greek origin "callipygian" indicates someone who has beautiful buttocks. However, the qualities that make buttocks beautiful or well-formed are not fixed, as sexual aesthetics of the buttocks vary considerably from culture to culture, from one period of fashion to another and even from person to person.

In ancient astrology, various parts of the body were associated with signs of the zodiac - e.g. the buttocks to the Balance. Depending on the context, exposure of the buttocks in non-intimate situations often causes feelings of shame, embarrassment or humiliation in a non-exhibitionist subject, and embarrassment or amusement in a non-voyeurist audience (see pantsing). Expressions such as being caught with one's pants/ trousers down or more explicitly in Dutch, "met de billen bloot" ("with bared buttocks"), use the image as a metaphor for non-physical embarrassment as well.

Willfully exposing one's own bare buttocks as a protest, a provocation, or just for fun is called mooning.

It is no coincidence that the English verb to spank is the only one specifically meant for physical discipline of a specific part of the body, and various other languages have terms specifically referring to spanking; in many punitive traditions, the buttocks are the preferential target for painful lessons, from educational to judicial, as offering them for punishment (especially divested) adds a psychological dose of embarrassment and even sexual humiliation to the pain, which can be meted out with less risk of long-term corporal harm than elsewhere. There are, in various cultural traditions, expressions like "seat of learning" which refer to the preferential paining of the posterior in a submissively bent and exposed position.