SACRUMS
Noun
sacrums
plural of sacrum
Source: Wiktionary
SACRUM
sa"crum, n.; pl. sacra (. Etym: [NL., fr. L. sacer sacred, os sacrum
the lowest bone of the spine.] (Anat.)
Definition: That part of the vertebral column which is directly connected
with, or forms a part of, the pelvis.
Note: It may consist of a single vertebra or of several more or less
consolidated. In man it forms the dorsal, or posterior, wall of the
pelvis, and consists of five united vertebræ, which diminish in size
very rapidly to the posterior extremity, which bears the coccyx.
Source: Webster’s Unabridged Dictionary 1913 Edition