It's similar to the word "shenanigans," but specifically meant for Coach Mike Shanahan.
1. It refers to the questionable or silly coaching decisions made by Mike Shanahan that negatively impact fantasy football owners who start NFL players that are coached by Mike.
2. It can additionally be used to describe the questionable or silly coaching decisions that negatively impact the NFL team in which Mike Shanahan coaches.
With less than two minutes to go the Redskins are down six points. Coach Shanahan decides to bench his starting quarterback Donovan McNabb, for whom he traded, in exchange for the back up quarterback who hasn't played in two years or normally practices with the Redskins' starting lineup.
This is Shanahanigans!
(This actually occurred in the 2010 Week 8 Redskins v Lions game on 10/31/2010)