To explain and clarify stupidity is not an easy task. Luckily though, a thesis of stupidity was created today by three individuals (only one of which frequents or contributes to this site). The news of this is great, for this has long been serious issue. So without further ado:
Stupidity according to the Lassen-Løvlie-Bjørvik-thesis: An individuals performance is qualitatively negative, relative to the actual or [a] given context.