[TA] a broad groove in the posterior cranial fossa, first situated on the lateral portion of the occipital bone, then curving around the jugular process on to the mastoid portion of the temporal bone, and finally turning sharply on the posterior inferior angle of the parietal bone and becoming continuous with the transverse groove; it lodges the transverse sinus. SYN: sulcus sinus sigmoidei [TA], sigmoid fossa, sigmoid groove, sigmoid sulcus.