mastoid emissary vein

n.
  1. A vein that connects the sigmoid sinus with the occipital vein or with one of the tributaries of the outer jugular vein by way of the mastoid foramen.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.