It means joy at someone else's misfortune. Only the Germans would have a word for that.
Jason Feifer over at The Morning News makes the point, at length, that although only the Germans do have a word for it we could all do with one anyway. The notion of schadenfreude being pretty universal.
Bonus: While at TMN check out the links to Profile of Popbitch, the email newsletter we can’t seem to unsubscribe from and Sixty-four versions of “Stairway to Heaven”.