Gunn's sign

n.
  1. An indication of arteriolar sclerosis observed ophthalmoscopically, in which the underlying vein at arteriovenous crossings is compressed.Marcus Gunn's sign
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.