When you perform some act that turns a previously-told lie into a truth.
A lies to B about going skiing in order to avoid going to a boring event. Later, A decides skiing sounds like a great idea after all, and does it, hence unlying about skiing.
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 $2 million.