sacrum

A triangular bone made up of five fused vertebrae and forming the posterior section of the pelvis.

A compound bone resulting from the ankylosis of two or more vertebræ between the lumbar and the coccygeal region of the spine, mostly those which unite with the ilia; the os sacrum.

That part of the vertebral column which is directly connected with, or forms a part of, the pelvis.

A large triangular bone located at the base of the spine between the two hipbones of pelvis and formed from fused vertebrae.

wedge-shaped bone consisting of five fused vertebrae forming the posterior part of the pelvis; its base connects with the lowest lumbar vertebra and its tip with the coccyx