A moment where a honky who supresses his racism has a verbal slip of tongue in which he makes a racist remark while not realizing he expressed his thoughts.

The word comes from the word Ku Klux Klan and the unpleasantness of a fart.
The South Park episode, where Stans Dad goes on Wheel of Fortune and shouts out nigger is a prime example of a Klan Fart.

The movie Clerks 2 where the meaning of porch monkey was confused in meaning was the funniest Klan Fart example I can think of.
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