sacrum

American  

[sak-ruhm, sey-kruhm] / ˈsæk rəm, ˈseɪ krəm /

noun

Anatomy.

sacra plural

1. a bone resulting from the fusion of two or more vertebrae between the lumbar and the coccygeal regions, in humans being composed usually of five fused vertebrae and forming the posterior wall of the pelvis.

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sacrum British  

/ ˈsækrəm, ˈseɪkrəm /

noun

1. (in man) the large wedge-shaped bone, consisting of five fused vertebrae, in the lower part of the back

2. the corresponding part in some other vertebrates

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sacrum Scientific  

/ sā′krəm,săk′rəm /

sacra plural

1. A triangular bone at the base of the spine, above the coccyx (tailbone), that forms the rear section of the pelvis. In humans it is made up of five vertebrae that fuse together by adulthood.

2. See more at skeleton

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Other Word Forms

Inflected Forms

noun

• sacra
  plural

Etymology

Origin of sacrum

1745–55; < Late Latin ( os ) sacrum holy (bone), translation of Greek hieròn ostéon

Compare meaning

How does sacrum compare to similar and commonly confused words? Explore the most common comparisons:

• sacrum vs. coccyx

Explanation

The sacrum is the large, triangle-shaped bone at the base of the spine. Many, though not all, animals with a backbone also have a sacrum. In humans, the sacrum sits wedged between the two hip bones, connecting the lowest vertebra of the spine with the tailbone or coccyx. A man's sacrum is slightly different from a woman's: it's taller and narrower, with a larger curve. The word comes from the Latin phrase os sacrum, or "sacred bone," and it was named this way because the large sacrum of animals was often a part of ritual sacrifices in ancient times.

Example Sentences

The fossil at the center of the study is a 22-kilogram Edmontosaurus sacrum, part of the dinosaur's hip region, recovered from South Dakota's famous Hell Creek Formation.

From Science Daily • May 14, 2026

Lonely Island member Jorma Taccone shattered his pelvis and detached his sacrum after a recent fall from a 20-foot ladder at his farmhouse in Connecticut.

From Los Angeles Times • Sep. 4, 2025

Woods said his sacrum had to be put back in place.

From Seattle Times • May 15, 2024

She curls into a ball, pounding her fists against the floor, and later balances on her sacrum, torso gently circling, in a resemblance of yearning or prayer.

From New York Times • Dec. 11, 2022

Pressing Pains: In forehead and occiput; with stitching in eyeballs; in eyes; on lungs; in sacrum.

From New, Old, and Forgotten Remedies: Papers by Many Writers by Anshutz, Edward Pollock

Related Words

• backside