sinus rhomboidalis
noun
sinus rhom·boi·da·lis
| \ -ˌräm-ˌbȯid-ˈā-ləs
\
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Medical Definition of sinus rhomboidalis
: the posterior expanded and for a long time incompletely closed part of the neural groove of vertebrate embryos
also
: an expansion of the central canal in the sacral region derived from it