Pelvic bones
'pelvic bones' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for sacra that I've seen before include "Bones that form the human pelvic arch" , "Triangular bones" .)
'pelvic bones' is the definition.
(I've seen this in another clue)
This is all the clue.
(Another definition for ilia that I've seen is " fused bones".)