Justin Baldoni's dropping a sex talk bombshell in his legal war with Blake Lively -- revealing notes from a crucial meeting about all the "It Ends With Us" sex scenes ... a meeting he claims Blake refused to attend.

The documents detail the director's April 21, 2023 meeting with an intimacy coordinator -- who was a woman -- to discuss how best to shoot the film's steamier moments. In his notes, Justin says it was important to have a female coordinator to craft sex scenes, because "It Ends With Us" fans are predominantly women ... so, he wanted it written for the "female gaze."

The notes, released Saturday on Baldoni's new website thelawsuitinfo.com, include x-rated language -- like, "goes down on her," "orgasm," "foreplay" and "the clit test" -- but Justin points out all of that came directly from the intimacy coordinator during their meeting.

FYI ... studios require these "intimacy" meetings for all productions shooting love scenes -- specifically to make sure all actors are comfortable, and to avoid sexual misconduct.

However, Justin claims Blake passed on the meeting. According to his amended lawsuit, "Ideally, these conversations would have taken place directly between Lively and the intimacy coordinator directly, as Baldoni had requested. However, Lively declined to meet with her, leaving Baldoni in the less than ideal position of having to relay these notes to Lively in her penthouse.”

Remember, Blake is suing Justin for sexual harassment ... but he's claiming the sexy conversations he had with his costar were merely him sharing the intimacy coordinator's notes. Interestingly, the phrases from the intimacy coordinator meeting are the same ones included in Blake's lawsuit.

Also, we've learned that raw footage showing BL and JB slow dancing -- which Justin's lawyer Bryan Freedman released last month -- was filmed almost exactly a month after the intimacy coordinator meeting Blake missed. That's important because Blake complained the scene wasn't choreographed with the intimacy coordinator.

As we reported, Justin believes the footage proves he was not sexually harassing her, and was merely an actor playing his part.

TMZ broke the story ... Justin amended his lawsuit Friday against Blake and Ryan Reynolds, and it included a complete timeline with ALL of his texts and emails regarding "It Ends With Us." Freedman has said they want complete transparency in order to defend Justin against Blake's campaign to destroy his career.