A common misspelling of the word average. So common that it has in fact taken on the definition of the word average.
It is also used to describe products that sell more than they should as the result of either being based on a prexisting licensed or commercial property, or by massive quantities of media attention. The term is most often used in reference to products of the video game and music industries.
"Chocobo Racing is very much an adverage game." "50 Cent: Bulletproof is adverage." "Doom is a super adverage movie."
A Shackteau is a humble, weather-beaten, structurally questionable shelter located in a spectacular or highly coveted place—Wales, Jackson Hole, Sun Valley, Crested Butte, coastal Maine, the Alps—where the building itself may be worth almost nothing, but the dirt, view, access, and mythology make it absurdly valuable.
In use:
Shackteâu - We thought it was an abandoned shed until the realtor called it a rare alpine Shackteâu with unobstructed views and listed it for $2million.