Kolaveri literally means Killer rage, or murderous rage. But then, the general usage of the word seems to have extended to any kind of rage, any anger. And here it's quite clear that the word (here) does not go in a very serious tone.
Besides, the song is called a 'Soup song' for 'Soup boys.' As per Dhanush himself, that means it's a song of failure in love, for boys who failed in love, a rejected boys' song.
And the interesting part is that though the song has words in Tamil, even if you don't know Tamil you get most of it, and can definitely enjoy it, provided you know the meaning of Kolaveri. So do listen.