MIA Share definition Flag Term for a person, preferably a girl, that always ends up really salty and her soul ends up being "missing in action" (hence the name MIA) My friend was such a MIA today because she got a 54 as her final average in Algebra. MIA by zuhazana September 4, 2017 0 0 Get merch Get the MIA mug. Buy Now β $32.95 See more merch