The mass media often uses the term "delusions of grandeur" to refer to a person who is in over his head, or who thinks exaggerates the amount of power and importance that he has. Used in the vernacular, the term usually describes people who are disliked dictators of countries, prominent businessmen, or celebrities, since they are often prone to being selfish and egotistical. However, this sort of popular attention downplays the seriousness of an actual medical diagnosis where symptoms are common in mentally ill persons.

Also generally known as megalomania, delusions of grandeur is a term familiar to psychological discourse. They are known as the manifestations of a psychopathological condition in which a person has delusional fantasies of power, wealth, and omnipotence, thus the term delusions of grandeur. Individuals may also bear an obsession with grandiose or extravagant things or actions. Despite evidence to the contrary, they may still be convinced of these false impressions.

In clinical terms, delusions of grandeur are real delusional symptoms, which are irrational and inappropriate beliefs. Often found in patients with varying degrees of either dementia, psychotic or depressive disorders, they firmly possess unrealistic beliefs that may eventually harm them physically, mentally, or emotionally.

Drug intoxication and drug addiction may also contribute to episodes of delusions of grandeur, especially when subject to the influence of marijuana or speed. This is dangerous because users who are high may believe they have powers that will enable them to perform dangerous feats that any normal human being would not succeed in doing, like flying off tall buildings or stopping an oncoming train with one hand. Delusions of grandeur could actually result in serious injuries or even death.

Like other clinical terms such as "anti-social" or "mentally retarded," the term "delusions of grandeur" is often used non-technically and incorrectly. While this behavior may downplay the negative social connotations of the phrase, it may mask situations in which actual delusions of grandeur bear an actual psychopathological threat to a person's health.