Jeannie Mai has responded to Jeezy's divorce petition, and she is more than insinuating he cheated on her and claims that will have a HUGE effect on their prenup and division of assets.

According to legal docs, obtained by TMZ, Jeannie more than insinuates her estranged husband is guilty of infidelity. Her lawyer writes, "Wife reserves the right to amend this counterclaim to add other grounds for divorce, but which Wife does not wish to specify herein at this time in the hope this matter can be resolved without having to disclose such conduct publicly."

But, it gets even more pointed ... "Wife further shows that the Court should enforce Paragraph 8 of the Prenuptial Agreement regarding infidelity which provides, in pertinent part, that in the event that either party engages in sexual relations, an emotional relationship, or is emotionally or sexually suggestive in communication with a third party via all forms of electronic communications, including but not limited to texting, sexting, Facetiming, social media and/or Direct Messages, shall result in a significant financial penalty upon the adulterous party ..."

In other words, she's accusing Jeezy of being unfaithful and claiming he's gotta cough up a bunch of dough as a result. The docs do not say who exactly Jeezy was allegedly banging, talking to, or seeing.

Jeannie coming out with cheating allegations is super interesting ... as we first told you, Jeannie was being accused of cheating on Jeezy with "Access Hollywood" host Mario Lopez, but a source close to her told us it was BS.

Jeezy, who filed for divorce in August down in Georgia, also released a 29-track double album, "I Might Forgive ... But I Don't Forget," in the wake of the split ... and it's highlighted by the song "Don't Cheat."

Cheating was also a theme Jeezy kept referencing during his recent interview with Nia Long.