confluence of sinuses

n.
  1. The dilated area at the internal occipital protuberance where the superior sagittal, straight, occipital, and transverse sinuses of the dura mater meet.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.