Lab Rat Meaning

(idiomatic) A person or group used as the subject of an experiment or test, especially unwillingly or unwittingly.

Example: 2013 April 8, Denise Grady, "Profiles in Science: Charting Her Own Course," New York Times (retrieved 20 April 2015):
  As a graduate student, she loved being a “lab rat,” Dr. Blackburn said, adding, “I was just really focused on the science, the science, the science.”
2012 May 1, Joanna Kakissis, "Greece's Former Prime Minister Assesses the State of His Nation," Time (retrieved 20 April 2015):
  Looking back at the unprecedented meddling of European powers in his country's politics amid the Euro crisis — a series of events that led to his fall as well as Greece becoming the first country in the zone to be forced to accept painful austerities in exchange for bailout loans — Papandreou told TIME, "I think it couldn't have been avoided. We were a lab rat, an experiment."
2012 Sept. 13, "TV Review: ‘Beauty and the Beast’," Washington Post (retrieved 20 April 2015):
  This time, Vincent . . . became an unwitting lab rat for a vaccine that turned soldiers into hyperaggressive killing machines.