Tyga just let the cat outta the bag!

The 25-year-old rapper, who's never been accused of being a rocket scientist, may have just inadvertently let the world know that he's engaged to 18-year-old Kylie Jenner.

In this video, Tyga looks at the camera and says, "I don't f—k with nobody. I f—k with nobody. It's just me, my fiancée, this lil' dog I just got. I f—k with nobody."

After seeing Ky walking around with a huge rock on her ring finger, we've speculated that the inappropriate duo got engaged after Kylie turned the big 1-8 -- but this is the first time we've heard either of them use the big "F" word (aka fiance/fiancee).

Kylie is the one who posted the vid from her Snapchat account so she must have wanted the world to know she was officially taken!

They could just be referring to each other as "fiancee/fiance" --or those could be pet names -- but umm that's weird and seems unlikely. It seems much more possible that the two are secretly engaged. Gag.

We have no idea how Kris Jenner is cool with her teenage daughter marrying a man who is seven years older, has an ex wife and a child -- but this is the woman who spawned all the Kardashian/Jenners -- her decisions are already suspect!