mun Share definition Flag 'mun' is like the slangish word 'man' and 'dude' only in a foreigh accent. Guy: Yo mun~~ Sandy: OMG YOUR ACCENT'S WIERD XD mun by Thegeocat September 30, 2005 0 0 Get merch Get the mun mug. Buy Now — $32.95 See more merch