Frumpy mumpy Share definition Flag A person who belongs to a certain crew who decides to wear shirt underneath jumper because it's 'fashionable' !!!! Her shirt is tooooooo big for her jumper. She is such a lumpy frumpy mumpy!!! Frumpy mumpy by bella spanish July 25, 2007 0 0 Get merch Get the Frumpy mumpy mug. Buy Now — $32.95 See more merch