Used to describe a retarded mountain goat but can be used to discipline small children
"Oh Dave your child is such a silly duffer"
by Dickmyeat August 5, 2015
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"silly duffer brother" or "SDB" for short can be used as a noun or adjective to describe an extremely idiotic person (also a nitwit or fool) or an extremely idiotic action.

SDB combines Aussie slang (duffer) and incorporates a reference to the world renowned Duffer Brothers (American twin brothers who write and direct science fiction films, horror films and television shows - including Stranger Things).
Girlfriend: "I can't find my phone again!"
Boyfriend: "It's in your hand you silly duffer brother (SDB)!"
by Horatio Bumbus July 27, 2017
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