Lindsay Lohan is pissed off with Paris Hilton -- claiming the shot Hilton fired at LiLo on a reality show was just plain "mean."
Lindsay is telling friends, "[Paris] is mean. You don’t have to make fun of serious matters in people's lives to be funny."
We posted the clip this morning from Hilton's new reality show "The World According to Paris" -- in which Paris gives a homeless woman her earrings ... and the woman mistakes Paris for Lindsay.
Paris responds -- "If I were Lindsay, I would be stealing earrings ... not giving them away."
This feud is so 2006.