messy marvin Share definition Flag "messy marvin"- person who masturbates and doesn't have the common curtesy to clean up their ejaculate. I often slip in jizz by the toilet, because my brother is a very messy marvin. messy marvin by mochox July 4, 2005 0 0 Get merch Get the messy marvin mug. Buy Now — $32.95 See more merch