The Mutant is a board from Naish.
Mutant because it looks like a twintip, but has on one end 4 fins like a directional and one end has one or two smaller fins like a twintip.
So if people talk about Mutant styled boards the are this mixture between TT and directional.

More info
http://www.naishkites.com/boards_produc ... age=mutant