pash-rash Share definition Flag a rash around the perimetre of the lips that is caused by pashing/snogging a guy/girl with facial stubble, resulting in a nasty ass rash. Karen came to school the next day with a scarf over her mouth because her pash-rash was so obvious pash-rash by Cricketa' September 22, 2005 0 0 Get merch Get the pash-rash mug. Buy Now — $32.95 See more merch