grot-chin Share definition Flag happens when a persons chin has been in miscellaneous sexual areas, which then results in a nasty red rash of the chin. when a girls chin goes near a dirty penis or anus the perpetrator may acquire grot-chin. grot-chin by KP&SP August 2, 2011 0 0 Get merch Get the grot-chin mug. Buy Now — $32.95 See more merch