marshmallowectomy Share definition Flag The process of removing only the marshmallows out of cereal or other product with marshmallows mixed in with it. I looked over at my son eating his Lucky Charms. He had executed a perfect marshmallowectomy. marshmallowectomy by Dyjital July 14, 2010 0 0 Get merch Get the marshmallowectomy mug. Buy Now — $32.95 See more merch