the unspeakable act of someone grinding on someone else's body while doing other sexual things. a synonym would be "dry-humping". This is not to be spoken of with family members or prude friends. Its nasty. Explicit. One of those things you just "dont talk about" x rated. careful, donking is not for everyone kids. Play safe! It is called donking because the butt (donk) tends to bounce around drawing all attention to it.
She was donking hard on that boy while they were making out on the couch. So public. I can't believe it.