Mumpsimus
Mumpsimus is a strongly adhered to custom although all the participants know it to be unreasonable.
A Mumpsimus is also a person who will continue with an error even after others have shown its mistake out of sheer bloody-mindedness or for fear of losing face.
Example usage:
“That mumpsimus knows using lime to sweeten the rice is stupid but he won’t stop because he hates being shown up by his students!”.
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