9 3/4 Share definition Flag 9 3/4 is the name of the train platform that any student attending Hogwarts School for Wizardry and Witchcraft. (Harry Potter series) To get to Hogwarts, we have to use platform 9 3/4. 9 3/4 by i.am.groot. April 20, 2017 0 0 Get merch Get the 9 3/4 mug. Buy Now — $32.95 See more merch