Barré's sign

[bă-rāz]
n.
  1. An indication of disease of the corticospinal tracts in which an individual, when placed in a prone position with the legs flexed at the knees, is unable to maintain a flexed position on the side of the lesion but can extend the leg.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.