Yes, "buttock" is a real word.
What is a Buttock?
A buttock is one of the two fleshy parts that form the lower and back part of the human trunk. The term is often used in the plural, "buttocks," to refer to both sides.
- Singular: buttock
- Plural: buttocks
The word is commonly used in anatomy, medicine, and everyday conversation, although sometimes people might use more informal terms.
Usage Examples:
- "She sat down, her buttocks sinking into the soft cushions."
- "The doctor examined the patient's buttock for any signs of injury."
- "The tailor adjusted the trousers to fit the buttocks properly."
The provided reference defines a buttock as: "Usually buttocks. (in humans) either of the two fleshy protuberances forming the lower and back part of the trunk." This confirms its legitimacy as a word in the English language.