Similar to Ebola, it's a crippling disease contracted from the stupid. Suffers will start to bleed from orifices until the brain is starved of oxygen for long enough it causes permanent brain damage. The suffer then spread the condition onto other uses creating an ever increasing circle of morons.
Contracting the disease can be as simple as being forced to sit within hearing distance of those already stupid enough that they are unaware of their own stupidity and blather on in incoherent ranting without the ability to shut their mouth and listen
I swear if this guy doesn't shut up I'm going to end up catching dumbola and being as retarded as he is.
In Quiz Bowl, the one object that a player is unbeatable to. Each player will have their own unique dumbwaiter, that they will always get, no matter how hard you study. This term is coined from the original "Dumbwaiter" drama by Howard Pinter, the dumbwaiter of Albert Ok of SLHS.
Albert: *buzz "DUMBWAITER!?"
Everyone else: "DAMN IT I READ THAT THINGYESTERDAY!"