1. having false beliefs that are not based in reality
Usage: psychology; medical
2. unreasonably believing something that is not true
Usage: informal

Examples

• The patient was delusional and believed he was a famous actor.
• She’s delusional if she thinks she can finish that project in one day.
• His delusional thinking made it difficult for him to maintain relationships.
• The doctor diagnosed her with delusional disorder.
• It’s delusional to expect perfect weather for the entire vacation.
• He became increasingly delusional after the accident.
• Her delusional beliefs about her abilities led to poor decisions.