A hybrid word of "gigantic" and "undies" used to describe only the largest, narstiest, granny panties on the planet. Typically of a cheap cotton/poly blend in a sad floral design. Usually found at Walmart for 88 cents hanging on those flimsy plastic hangers.
I was at my grandma's house, and I found her dirty gigundies behind the couch. What were they doing there? Ew!