sacralization
noun
sa·cral·iza·tion
| \ ˌsā-krə-lə-ˈzā-shən
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variants:
also British sacralisation \ -ˌlī-ˈzā-
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Medical Definition of sacralization
: incorporation (as of the last lumbar vertebra or any of its parts) into the sacrum
specifically
: a congenital anomaly in which the fifth lumbar vertebra is fused to the sacrum in varying degrees