The Collaborative International Dictionary of English v.0.48:

Anticoherer \An`ti*co*her"er\, n. (Wireless Teleg.)
   A device, one form of which consists of a scratched deposit
   of silver on glass, used in connection with the receiving
   apparatus for reading wireless signals. The electric waves
   falling on this contrivance increase its resistance several
   times. The anticoherer can be used in conjunction with a
   telephone.
   [Webster 1913 Suppl.]