Similar to planking, except significantly less ghey (and Xzhibit doesn't seem to have any issues with it). Specifically, when one is caught and/or photographed sleeping on the job, particularly in the backstage area on the couch at UK Thursdays. However, it is also acceptable to refer to any sort of nap as a "taking a Crit".
"Did you see Greg backstage? Grab your camera, he's totally Crit-ing hardcore."