From the English nouns "eunuch" and "cycle", a eunuchcycle is a bicycle or other form of saddled transportation (exact nomenclature dependant on method of transportation in question), which, upon continuous usage leaved the testicles of the male rider severely bruised or eroded completely. This may also apply to less prolonged exposure to a thoroughly unsuitable saddle, perhaps one made of sandpaper or some other high-friction material.
"I've just been for a 40 mile bike ride and I feel GREAT!"
"Wow, that's fantastic, man! Bet your balls hurt, though"
"Oh dude, they are killing me, I think I might have punctured one!"
"You need a new bike, that one you have at the minute is a total eunuchcycle"