Other forms: zonked; zonking; zonks
To zonk is to hit someone hard, the way the mouse zonks the cat in his head over and over in the classic cartoon Tom and Jerry.
The verb zonk started as a slang term inspired by the sound that might result from bashing or clobbering someone. It's also used to describe the stupefied or stunned result of being zonked in the head: "He'll zonk out for a while after getting tackled in the football game." Or you can use it for something that stops working abruptly: "My laptop zonked out, so I couldn't do the homework!"