Iggy Azalea Gives Booing Fans the Finger

Who dat, who dat ... it's I-G-G-Y ... and she's flipping off her fans.

Iggy Azalea was heading into the NYC Jingle Ball event Friday night at Madison Square Garden when she gave her fans the brush off ... which did not sit well and trigger a chorus of boos.

That's when the "Fancy" rapper fought back ... giving a serious bird to the frustrated crowd.