microdot definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
a microcopy of pinhead size, used in espionage, etc.
Origin: micro- plush dot
microdot definition by American Heritage Dictionary
A copy or photograph that has been reduced to an extremely small size for ease of transport and purposes of security.