Elon Musk Calls Elizabeth Warren 'Sen. Karen,' She Blasts His Person of Year Honor

Elon Musk and Sen. Elizabeth Warren are going at it -- their war of words is erupting, and it's all over TIME naming him Person of the Year, or as she would put it ... "Freeloader of the Year."

The U.S. Senator from Massachusetts fired the first shot across the bow ... calling out Musk for -- as she sees it -- not paying enough taxes. She tweeted Tuesday, "Let's change the rigged tax code so The Person of the Year will actually pay taxes and stop freeloading off everyone else."

The world's richest man quickly responded to Sen. Warren, saying ... "You remind me of when I was a kid and my friend's angry Mom would just randomly yell at everyone for no reason."

He got even more personal, claiming Warren is simply projecting when she accuses him of ripping off taxpayers.

We've heard Sen. Warren issue this same grip before ... earlier this year she ripped another billionaire space guy (and former richest man), Jeff Bezos, for not paying enough income tax, while sinking billions into his space program.

Both Musk and Bezos have pointed out they're only taking advantage of the very tax code Warren and the rest of Congress created.