Iggy Azalea Threatens Nick Young ... I'LL CUT OFF YOUR PENIS

Nick Young is on the THINNEST of ice -- 'cause Iggy Azalea says if the NBA star betrays her just one more time, SHE'LL GO FULL LORENA BOBBITT ON HIS ASS!!!

Iggy appeared on the "Orlando & The Freakshow" radio show on Wild 94.1 -- and made it clear she's very NOT COOL with what she saw in D'Angelo Russell's video ... when Young apparently admitted to cheating on her.

"I'm not cool with it," Iggy said ... "Like you'll have half a penis."

"I already said one more video, just one more thing and you will lose a quarter of your meat."

There's A LOT more ... when the radio host brought up the bro code violation between Nick and D'Angelo -- Iggy said, "screw guy code."

"I have an actual spoken commitment that you're going to get married to me ... and that involves not doing any of those other things."

Iggy finished the interview by going full ALPHA FEMALE -- saying when it comes to fans, she's got WAY MORE than Nick.

For the record, they're still engaged ... but it's pretty obvious Nick's still in the dog house.