Yes, but still,’ said Hermione, with an air of explaining something very simple to somebody very obtuse, ’even if you do cause a diversion, how is Harry supposed to talk to him?
He was halfway along the corridor outside when he heard the unmistake-able sounds of a diversion going off in the distance.
They exchanged a look of great surprise, but Harry did not have time to feel awkward or embarrassed; his knees were becoming sorer by the second and he guessed five minutes had already passed from the start of the diversion; George had only guaranteed him twenty.
…during the next summer holidays he would have a chance to ask Sirius about the scene he had witnessed in the Pensieve… nothing, except that the thought of taking this sensible course of action made him feel as though a lead weight had dropped into his stomach… and then there was the matter of Fred and George, whose diversion was already planned, not to mention the knife Sirius had given him, which was currently residing in his schoolbag along with his father’s old Invisibility Cloak.
There are no more uses of "diversion" in the book.
Show samples from other sources
The attack on the capital was actually a diversion to draw troops away from the port city.
And I’d bet my broomstick he let that troll in, to make a diversion!
J.K. Rowling -- Harry Potter and the Sorcerer’s Stone