To be fucked in the ass so hard without lube (either literally or figuratively) that you are never the same again.
"After giving his brother a Morning Wake-up Call, he was completely Wallstered when his brother retaliated by pouring a gallon of sac soup on him while he was tossing the dwarf to some kids program on tv.
A progression of the nickname Wullie, often the nickname is a natural follow on from wullie to wullster in later years of ones life. Many nicknames find the "ster" tag added as we grow up.
As a boy we called him wullie but at some point around the drinking and shaggingpart of our lives it changed to wullster.