Frey's irritation hairs

[frīz]
pl.n.
  1. Short hairs of varying degrees of stiffness that are embedded at right angles into the end of a light wooden handle and are used for determining the presence and sensitivity of pressure points of the skin.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.