The "No return" maneuver
When you're bored in class or at dinner, and start leaning back in your chair, but you do it a bit too far and reach the point of "no return". At this point you fall flat on your arse, while everyone is laughing at you, because everyone noticed the ear-deafening bang you created falling.

Also can be applied to when you're busting a nut.
When we were sitting at dinner, Shaniqua was bored and was leaning back, and she leaned back too far and suddenly she reached the point of no return, and fell.

I've reached the point of no return, I'm about to nut

I couldn't submit this without defining the word, so The "No return" maneuver means falling on your ass while sitting in a chair.