Looks to me like the guy backing away has probably been jabbing and moving and the guy doing the wierd move is frustrated and trying to shame his opponent into getting in close. The arm he's got folded up is ready to twist round and make a quick grab.
Apparently none of you assholes saw the match. That was a mock gesture made to lampoon the fact that Kalib Starnes entered the Octagon and elected not to engage. That gif is in no way indicative of MMA as whole as Kalib Starnes was both booed for his reprehensible behavior by the audience and released from his contract by the organization.