To hold the ball longer than is required to take four steps.
This is the type of shyte that make the Offical Guide a laugh. If you're standing still, the time to take four steps is infinity. If they mean the time required to take four steps if you weren't standing still, what sort of nonsense is that? If your imaginary steps (that you're not taking, remember) were running-flat-out steps, the time to take four of them might be 0.75 of a second. But the referee might be imagining walking steps, as the rules don't tell him otherwise. Four of those might take 3 seconds.