Name used to describe someone who often does very normal things in crazy, insane, or unpredictable ways. Sometimes these people may confuse you by doing something normal one second and then doing the very same thing in some wacked out way the next second. An easy way to spot a Mullis is thier unique way of playing poker which causes them to either loose horribly in the first few hands OR confuse the other players so as to cause them to fold everytime the Mullis bets due to the unpredictability of the hand being bet on.
While playing poker, Matt went all in as he has done many times before. The other players all fold their hands. Matt reveals that he had absolutely nothing of any value in his hand. One player yells "I should have known he didn't have anything because he's a fucking Mullis!"