When you take a huge hit off of a joint, blunt, bong, bowl, etc. to the point where you cough uncontrollably. You can feel a goncho hit when when smoking out of a bong as the back of your throat starts burning before you pull the slide.
"Dude, just take a goncho rip off of that and pass it back"
"Hey Tyler, you wanna get gonchoed before the steelers game?"