One my my friends got a Diamond cut out symbol tattooed on her fore arm, what does it exactly mean? or is it just a diamond?

Pictures of the diamond:
http://ny-image2.etsy.com/il_fullxfull.95137434.jpg
http://media.photobucket.com/image/diamond%20cut%20out%20tattoo/slytherin123/hate%20to%20label%20but%20these%20r%20just%20some% 20sceneish%20kids/3328l.jpg
http://www.avidhuman.com/img/chuck_tattoo.jpg