Delusional Meaning: Here’s What It Means And How To Use It

Here is the complete guide to the word delusional’s meaning. Never wonder about definitions, history, synonyms, or examples of this word ever again.

Your writing, at its best

Compose bold, clear, mistake-free, writing with Grammarly's AI-powered writing assistant

Today, we’re going to walk through a complete guide to the word delusional. By the end, you’ll be familiar with the definition of the word, its etymology, and how it is commonly used in language and writing. So, let’s dive into the word delusional and give you the tools you need to incorporate it into your speech and your writing.

The Definition of Delusional

The root word of delusional is the word delusion. In order to understand it correctly, first let’s look at the definition of delusion according to the dctionary. 

As a noun, it refers to a belief somebody has that is incorrectly believed or propogated.

In psychiatry, it is a false psychotic belief — either about yourself or others — that you maintain despite indisputable evidence proving it wrong.

As a noun, it can also mean the state of being deluded, or it can be the action of tricking someone into believing a delusional concept.

If those are the meanings of delusion, then the word delusional is an adjective that describes somebody who is inflicted with a delusion.

 Delusional can be used in an informal context to describe a person who is misguided or grossly deceived. In this context, a person who is delusional has a false belief or set of delusional beliefs that alter their behavior, despite those beliefs being unreasonable or demonstrably false. 

In Psychiatry

The word delusional can also be used in a formal medical context for healthcare professionals to describe a person with diagnosable psychological disorders that lead to psychosis, such as schizophrenia, Alzheimer’s, bipolar disorder, delusional disorder, or another mental illness.

According to the 5th edition of the diagnostic and statistical manual of mental disorders, or DSM-5, Delusional Disorder is the presence of one or more delusions with a duration of one month or longer. These symptoms often include delusions of persecution or the belief that a person or entity is out to get you or constantly working against you. 

These persecutory delusional symptoms can cause anxiety and paranoid behavior that can affect a person’s career, relationships, and loved ones. It is often treated with psychotherapy like cognitive behavioral therapy (CBT). That is one example of delusions, but many different types of delusions can exist in a person with this medical condition.

The Ancient Origins of Delusional

The word delusional has an incredibly long history, stemming beyond Middle English and Old English and gaining its roots from Latin. The Latin word deludere or deludo means “to mock or deceive.” 

This gave rise to the Middle English word deluden, which had a similar definition to the modern word delusion. It is unknown when the Middle English word was developed, but the first instance of the modern English word delusion did not come about until the 15th century. 

Examples of Delusional in Context

It’s important to remember that the word delusional has different meanings based on the context. In an informal context, it can be an exaggeration that somebody uses to express they believe a person is misguided or crazy. The word delusional has much more serious implications in a medical context, such as a specific mental health diagnosis. 

Here are some examples of both contexts: 

I’ve been avoiding him all week, so if he thinks I want to talk to him, then he must be delusional.

My delusional uncle believes all of these conspiracy theories no matter how many times I refute them with hard evidence.

The patient believes he is being followed by a ghost, and it has been affecting his relationships for the past month. I am diagnosing him with delusional disorder.

The patient’s hallucinations lead to delusions and disorganized behavior, so I think schizophrenia is a fitting diagnosis. 

What Are Synonyms of Delusional?

There isn’t really a synonym or antonym for the medical version of delusional, but the casual definition definitely has some synonyms in the thesaurus: 

  • Confused
  • Unrealistic 
  • Confused 
  • Deceived 
  • Misguided

What Are Common Forms, Sayings, and Phrases of Delusional?

The word delusional comes in a lot of different forms in real life. There’s also its noun form, delusion. Also, the adjective delusionary is specifically meant to describe ideas or opinions rather than a person. Then, there is the verb, delude, or to delude. This refers to the action of deceiving somebody with a delusion. 

One of the most common uses of this word is in the phrase “delusions of grandeur.” This saying refers to incorrect beliefs about how important a person is or how much status they have in a certain context. The phrase first entered use in English in the late 19th century. 

The first recorded use of the word was in the court case of a tailor named H.P. Cooper. His brother had accused him of being insane and having delusional thinking, and the case was taken to court. Cooper was accused of insanity and delusions of grandeur about his hopes of developing properties in New York. 

The saying is often confused with megalomania, but the two are slightly different. Delusions of grandeur are mistaken beliefs that you are more important than you are. Megalomania is a psychological condition that causes a person to be obsessed with power and control. So the two are distinctly different. 

A Common Word with Many Subtleties

The word delusional is an incredibly useful word, but it can have certain unintended implications if used incorrectly in the wrong context. But now you have a sturdy understanding of the word and how to use it. Consult this article again if you need a refresher, but now you’re ready to go use delusional in your writing, grammar, and speech.


  1. Delusional Meaning | 
  2. The meaning and origin of the expression: Delusions of grandeur | The Phrase Finder 
  3. Table 3.20, DSM-IV to DSM-5 Psychotic Disorders – Impact of the DSM-IV to DSM-5 Changes on the National Survey on Drug Use and Health | NCBI