delusion

noun

1. (countable, uncountable)An adamant belief in a falsehood despite incontestable evidence.
2. (countable, uncountable)The state of being deluded or misled, or process of deluding somebody.

   “It is far better to grasp the universe as it really is than to persist in delusion, however satisfying and reassuring.”

3. (countable, uncountable)That which is falsely or delusively believed or propagated; false belief; error in belief.

   “Hess, always a muddled man though not so doltish as Rosenberg, flew on his own to Britain under the delusion that he could arrange a peace settlement.”

   ““Project Greenlight,” however, bore down on the soft underbelly of the movie business, focusing on the delusions and colossal blunders of first-time directors, seemingly selected as much for their unlovability as their talent.”

4. (countable, uncountable)A fixed, false belief, that will not change, despite evidence to the contrary.