The Tesla chief tweeted an insult at the Microsoft co-founder Friday, posting a side-by-side photo of BG next to an emoji of a pregnant man ... a new one that was recently rolled out to be more inclusive to trans men. Elon's caption ... "in case u need to lose a b***r fast."

He followed up by jokingly tweeting a picture of cloaked figures coming together in a circle and writing, "shadow ban council reviewing tweet …" seemingly aware his OG tweet might be seen as offensive. It's also undoubtedly connected to his current bid to buy Twitter.

Of course, some were confused about the shot in the first place ... but leaked texts between Elon and Bill seem to paint a clearer picture about what's going on.

No word on when this convo happened, but Elon himself confirmed the texts are legit ... saying they'd apparently been leaked to the NYT by friends of friends. He adds, "I heard from multiple people at TED that Gates still had half billion short against Tesla, which is why I asked him, so it’s not exactly top secret."

If you peep the texts, it shows Elon and Bill going back and forth ... apparently trying to set up a meeting of some sort -- one in which BG wanted to talk philanthropy and climate change. Before that, though, Elon asked him straight up ... you shorting my company, bro?

Elon's angry that Bill's betting against Tesla's stock ... placing a major wager that the price will dip. Elon also argues that Tesla is doing a lot to mitigate climate change by investing in sustainable energy, so he sees Bill's position as hypocritical here.