What does the word delusion mean?

Usage examples for delusion

  1. The poor man is under a strong mental delusion, he cannot act in the least; however, we shall see what he will do with " Venice Preserved." – Records of a Girlhood by Frances Ann Kemble
  2. Unless he is living under the power of some strong delusion, he knows that he is not worthy of regard. – The True Citizen, How To Become One by W. F. Markwick, D. D. and W. A. Smith, A. B.