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2.
A miserable person. Someone who never smiles or has fun, usually an old person.
"Here he is, the fuckin' old misery guts!"
by Klausey September 15, 2009
 
1.
A word describing a person who is against having any sort of fun at any time.
Man #1: "No hanging off the chandelier!"
Man #2: "Miseryguts!"
by xcarex June 28, 2007