sacral vertebra

English Thesaurus

1. one of 5 vertebrae in the human spine that fuse in the adult to form the sacrum (noun.body)

hypernym	:	vertebra,
definition	:	one of the bony segments of the spinal column (noun.body)

part meronym	:	sacrum,
definition	:	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 (noun.body)