This is my Dad's joke:
"Zenophobia: the fear of the sound of one hand clapping." Ha! ha! Hahahaha!
Don't get it? Don't feel bad. Funker, it took you being nonplussed for me to realize how sophisticated this gag is...
The Zen Buddhists are notorious in popular culture for their koans, succinct pithy riddles with no real answers, that they meditate on (supposedly) to still the bustle of everyday thought. A good example would be, "If a tree falls in the forest, and there's no-one there to hear it, does it make a sound?"
The most cliched of all is "What is the sound of one hand clapping?" (In fact, both of the koans I cite have been spoofed on the Mini-golf episode of the Simpsons.)
Zenophobia sounds like a legitimate word because it is homonymic (sounds identical) to xenophobia, a real word meaning bigotry or fear of foriegners.
Zenophobia: the fear of the sound of one hand clapping.