(As if Hungarian language needed anything extra to mindf*** non-English speakers...)
Eszperente (a play on Esperanto) is a language-within-a-language: It means someone making coherent sentences with only one vowel (e) in them. Since Hungarian as a language contains an overabundance of words that only contain e, it is actually possible to have long conversations, or create long monologues, without using any other vowel in the entire thing.
(This is especially funny because Hungarian language also happens to have an overabundance of vowels: a, á, e, é, i, í, o, ó, ö, ő, u, ú, ü, ű - it's not like we are limited to "e")
It is a form of a language game for people to try to converse in eszperente - whoever trips into another vowel first loses the game.
The blog Daily Magyar even took the game one step further:
And in case you are curious how this actually sounds, here is an entire rap song in eszperente:
Try it in your own language. See of it works.