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1.
To dun or don't understand.
I dunderstand what you're driving at.
by maltar January 06, 2011
 
2.
(v) To believe you have great insight or comprehension of a word, concept, or situation but to be entirely wrong about it (i.e., eisegesis). Portmanteau of "dunder" and "understand".
He thinks golden showers are all about gold coins. That's some serious dunderstanding.
by Talmanes December 20, 2013