Paulie was old and tired of cutting hair for the same people over and over, listening to their sob stories all the while. So he drank that blue stuff on the counter and committed barbicide.
The act of destroying a person's psyche and/or will to live by means of incredible rapping performance, whether by devastating insult to the person affected or by pure lyrical genius.
*Rapper finishes his set of amazing rhyming*
Victim: I...I can't go on. LIFE SIMPLY ISN'T WORTH LIVING ANYMORE!