mumpsimus

/ˈmʌmpsəməs /

Definitions of mumpsimus

1. noun

   a clearly mistaken, unreasonable, or outdated belief or practice that is stubbornly adhered to
   “he still holds to the old mumpsimus that a woman's place is in the kitchen”

   type of:

   notion

   a general inclusive concept
2. noun

   (rare) a person who stubbornly refuses to correct a proven mistake or change an outdated belief or way of doing something