buttock

Inherited from Middle English buttok, probably from Old English buttuc (“end; end piece”; also, “short piece of land”). Attested with its current anatomical meaning since 1300. A diminutive form of what is presumably the Old English precursor of butt +‎ -ock (diminutive suffix).

• (UK) IPA^(key): /ˈbʌtək/, [ˈbɐtək]
• (US) IPA^(key): /ˈbʌtək/, [ˈbəɾək]

• Audio (US)

  (file)

• Rhymes: -ʌtək

buttock (plural buttocks)

1. (usually in the plural) Each of the two large fleshy halves of the posterior part of the body between the base of the back, the perineum and the top of the legs.

   Synonyms: (crude) asscheek, cheek; see also Thesaurus:buttocks

2. (nautical) The convexity of a ship behind, under the stern.
   • 1925, Adventure, volume 54:

     There came a blast of freezing wind that made Skell shrug himself against the oaken post on which the ship's buttock rested.

• The plural form is usually used in the singular sense for a single person’s posterior, often informally called butt (North America) or bum (Britain). It is rarer to refer to only a single buttock, which is then usually specified as left or right.

• callipygian/callipygous
• dasypygal

• Webster's Seventh New Collegiate Dictionary, Springfield, Massachusetts, G.&C. Merriam Co., 1967
• Douglas Harper (2001–2023), “buttock”, in Online Etymology Dictionary.