When you spend a good deal of time in the sand, whether it be at the beach or other sandy areas, and you come to realize that you have sand caked up in your lower groin. It creates a noticable discomfort known as "dune crotch."
"I should've taken a shower, I've got such bad dune crotch.."
Dune digga dune is used to describe someone who is overweight or fat. It is derived from the opening theme of the cartoon "Fat Albert" when the bass line first starts making the sound "dune digga dune digga dune digga dune" followed by the unforgettable "hey hey hey, its faaaat Albert".
sitting in the chinese buffet restaurant: "man look at all these dune digga dune's."
walking in the mall and seeing a fat person, points finger: "dune digga dune"
damnjeff, you need to start exercising, you're becoming a real dune digga dune.