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1.
A term used to describe a person with downsyndrome. Can also be used to describe a person which behaves like a Retard.
"Check out the moon belly with the snow cone."

"Scott was such a flippin moon belly at the Christmas party. I wanted to kick him in the jimmies."
by MoonBelly September 30, 2005
 
2.
When someone has a beer belly gut that looks like the shape of the full moon.
"mitch has a moon belly, wolves howl when he shows his gut"
by robvandammage April 25, 2010