warchalk

from The Free On-line Dictionary of Computing (8 July 2008)

warchalk

   <networking> A system of runes and annotations chalked on
   walls or other surfaces to indicate to interested parties the
   presence of a {wireless} network {node} in the vicinity.

   Warchalking was inspired by "hobo language" - the signs used
   by American itinerants during the Depression years to indicate
   where they might find a meal.

   (http://blackbeltjones.com/warchalking/).

   (2002-06-26)