This is not okurrrr -- Nicki Minaj dragged Cardi B's daughter Kulture into their feud when they were trading barbs online Tuesday ... and things got messy.

Check out the tweets -- it all started Monday when Nicki began talking trash Cardi's new album, "Am I The Drama?" It got personal when Cardi hit back and accused her foe of "going to different fertility doctors cuz you couldn’t reproduce from all them percs scrambling your eggs."

Minaj clapped back, denying she's ever "seen or spoken to a fertility doctor" ... and even threatening a lawsuit.

The drama hit a boiling point on Tuesday, when Nicki reiterated her "Barney B" nickname for Cardi ... and came up with one for her daughter, labeling her "kulture vulture? Not long after, she spoke directly to Cardi's oldest kid, writing ... "Kulture vulture you ugly too."

That's when Cardi went off, warning the "Anaconda" singer this will be the final time she says her kids' names ... or she'll "spill the tea" about her family.

She swiftly added ... "B*tch you wish you could call my daughter ugly.. Kulture is beautiful and you know that." In the same tweet, she accused Nicki of halting her son's growth by giving him some sort of drugs.

They also started talking smack about each other's relatives ... you can see it all in the eye-popping tweets.

As you know ... Cardi and Nicki have been feuding for years -- even once nearly beating each other up at a 2018 New York Fashion Week event after Cardi threw a shoe at her nemesis.

The mother of 3 with one on the way recently addressed her drama with Nicki on "Call Her Daddy" ... denying she is an industry plant whose goal was to replace Nicki.

She noted that sometimes, women in the rap game simply don't mesh -- and that couldn't be more obvious!