It happens a lot: a receiver catches the ball, drops it, it is called a fumble on the field. Then there is some expert commentator giving his opinion on whether the receiver made a 'football move' after catching the ball.
It came up with Texans v Colts this year. Johnson's drop was called a fumble, a talking head confidently stated it would be reversed because Johnson clearly didn't have possession and make a football move. It was not reversed. This happens a lot.
Is this term 'football move' defined anywhere in the rule book? Are there explicit criteria to be applied? I looked in the online version and didn't find anything: