Zen happens

Wikipedia is my best friend on the Internet. According to my best friend on the Internet, Zen is actually a school of Buddhism that encourages people to meditate and try to attain enlightenment by themselves, without referring to sacred texts too much. I like this way of thinking, it's similar to my own: direct experience is always more useful and more convincing than theoretical knowledge.

The next bit is a bit weird though. It says there are several stories which really are more part of Chinese and Japanese folklore than Zen philosophy. Here's an extract of the first one:

"The origins of Zen Buddhism are ascribed to the Flower Sermon, the earliest source for which comes from the 14th century.^[1] It is said that Gautama Buddha gathered his disciples one day for a dharma talk. When they gathered together, the Buddha was completely silent and some speculated that perhaps the Buddha was tired or ill. The Buddha silently held up a flower and several of his disciples tried to interpret what this meant, though none of them were correct. One of the Buddha's disciples, Mahākāśyapa, silently gazed at the flower and is said to have gained a special insight directly from the Buddha's mind, beyond words. Mahākāśyapa somehow understood the true inexpressible meaning of the flower, smiled and the Buddha then acknowledged Mahākāśyapa's insight [...]"

You're part of a sort of small, harmless religious sect. It suits you, they don't ask you for money, they don't try to convert people against their will etc. Your teacher calls you and your fellow religious together and just sits there for a while. The silence grows long and awkward. A few people cough. Just as someone near the front is about to poke him or say something, he lifts a hand. In his hand is a flower. A few people sigh in relief and everyone stares at the flower, waiting for him to speak. He doesn't. Someone takes the initiative and says something like, "does the flower symbolize the ephemerity of life?" but your teacher shakes his head. A second person suggests something else, and a third. People are getting into it, thinking really hard about the meaning of the flower. Then the teacher looks at one of your collegues near the front, someone who is smiling the kind of smug smile that makes you want to punch them in the teeth. Your leader points at him and says, "he's got it". Everyone turns to the man expectantly. Then your leader says, "don't expect him to tell you. It's beyond words. You have to attain enlightenment, and you have to do it by yourselves. Ha!"

Well, he doesn't say "ha", but you all hear him thinking it very loud. As you all file out of the room, some people mutter that that guy was always the favourite anyway, and that it was all probably a set-up. Five people quit.

With all this in mind:

"Zen - What is the sound of shit happening?"

... my only interpretation of this is that meditation techniques often include concentrating on something, an image or a sound. Repetitive sounds are particularly good. Eww.