deceptive fisting
A rule in Muggle Quidditch in which the beaters of a team claim immunity by putting their fist in the air when immunity cannot be claimed, i.e. when their teammate already has a bludger or the opposing team does not have 2 out of the three bludgers in possession.
That beater put up his fist even though his partner had a bludger! That's deceptive fisting!