What does the title of the anime "K" mean? In 2012, there was an anime titled K (or sometimes K Project). Does the title mean anything in the context of the anime? 

(cf. C, which was titled for the word "Control", and X, which was supposedly titled after the use of the letter "x" as a variable).
There are two possibilities for what the "K" refers to.

The first is Adolf K. Weismann, who is the original person that became Yashiro Isana, the main character of the show.

The second is "King". The leader of each clan is its King, who controls the members of the clan.  Weismann is a King.

KINGS is also the first opening theme of the show.