To shake the face violently from side to side for the purpose of humour. This moment is performed for the camera to break up the monotony of the scenic photos. It can be classed as pure genius entertainment.
The skill of shaky-face is to simply relax the face completely. Look in the direction of the camera and shake as hard as you can. Many people fail to achieve shaky face ninja status. You can see the act on many facebook groups such as "Shaky face Ninjas".
by Scott Clifford August 18, 2007