A supposedly-unavoidable mental/emotional condition wherein the "sufferer" cannot speak civilly, remain calm, or otherwise conduct himself in a reasonable/socially-responsible manner unless he is being constantly entertained or excited. Usually there is in fact nothing whatsoever truly wrong with the cranky person's mind, and thus his "illness" merely stems from a petulant selfish mindset that probably resulted from his being pampered and spoiled rotten as a child.
Teenage delinquent: Things are gettin' a little boring around the 'hood --- let's incite a riot!
Responsible teenager: Sorry, pal... I ain't gonna jeopardize my 100% clean criminal record just to temporarily satisfy your boredomline personality disorder!