Definition of hallucination

Short definition: The word hallucination means an experience where a person sees, hears, or feels something that does not exist in reality. People use it to talk about mental or physical conditions, extreme stress, or moments when the brain creates sensations that feel real but are not.

Looking for a clear and natural explanation of the word hallucination? The word hallucination is often used when talking about seeing, hearing, or feeling things that are not actually there. It can sound scary, but hallucinations can happen for many reasons, from lack of sleep and high stress to illness or certain medications. In everyday conversation, people sometimes use the word more loosely, to describe strong imagination or moments that feel unreal. Below, each meaning is explained in a calm and natural way, so it feels human and clear, not overly medical or cold.

Noun forms: hallucination, hallucinations
Related: hallucinate v., illusion n., delusion n.
Syllable: hal-lu-ci-na-tion

1. Seeing, hearing, or feeling something that is not actually real.

   In its main meaning, a hallucination is a sensory experience that feels completely real, even though nothing is really there. A person might hear voices, see shapes, or feel touches that no one else can sense. For the person experiencing it, the moment feels true, which can be confusing or frightening.

   He described the voices as a hallucination that felt real in the moment.
   During the fever, she experienced a strange hallucination.
   Doctors explained that the hallucination was a side effect of the medication.

   Synonyms: false perception, imagined sight, unreal experience, sensory illusion, phantom vision, imagined sound, unreal sensation, mind-created image, perception error, false sensory experience, mental image, unreal feeling
   Antonyms: reality, clear perception, real experience, true sight, accurate sensing, normal awareness, genuine feeling, real sound, actual vision, true perception, grounded experience, real awareness

2. A symptom linked to illness, stress, or lack of sleep.

   Hallucinations can happen when the body or mind is under extreme pressure. High fever, exhaustion, mental health conditions, or strong medication can all affect how the brain works. In these cases, hallucinations are a signal that something in the body needs attention and care.

   Severe sleep loss caused short hallucinations for the patient.
   The doctor explained that the hallucination was stress-related.
   After rest and treatment, the hallucinations stopped.

   Synonyms: stress symptom, illness sign, brain response, mental strain effect, exhaustion reaction, fever-induced vision, medical symptom, health-related perception change, body warning sign, mind overload response, condition-related experience, treatment side effect
   Antonyms: mental clarity, healthy perception, normal awareness, stable mind state, clear thinking, physical well-being, balanced condition, grounded awareness, healthy response, stable senses, mental calm, clear consciousness

3. A moment of strong imagination that feels real.

   Outside medical talk, people sometimes use hallucination in a lighter way. They might say something felt like a hallucination when they were extremely tired, shocked, or surprised. In this sense, it doesn’t mean illness, but how strange or unreal the moment felt.

   After staying awake all night, he joked that everything felt like a hallucination.
   She said the bright lights felt like a hallucination after the dark flight.
   Winning the prize felt so unreal it was like a hallucination.

   Synonyms: unreal feeling, dreamlike moment, strange experience, surreal moment, imagination run, mind trick, fantasy-like scene, unreal sensation, shocking moment, dream-state feeling, odd perception, strange illusion
   Antonyms: grounded feeling, normal experience, clear moment, ordinary perception, real-world feeling, practical awareness, everyday sense, down-to-earth moment, solid reality, plain experience, clear-headed state, real-life moment

4. Something that shows how powerful the mind can be.

   A hallucination also reminds people of how strong the human brain is. The mind can create sights, sounds, and feelings that seem real even without outside input. This meaning often appears in psychology and discussions about human perception.

   Scientists study hallucinations to understand how the brain works.
   The documentary explained how the mind can create hallucinations.
   Learning about hallucinations changed how she understood perception.

   Synonyms: mind power example, perception mystery, brain-creation moment, mental phenomenon, perception puzzle, mind-made experience, cognitive illusion, brain-response case, perception science example, mental-process sign, awareness study topic, psychology case
   Antonyms: physical certainty, external reality focus, real-world input, sensory accuracy, objective perception, physical experience, real-environment response, grounded awareness, factual experience, clear sensory input, reality-based perception, external truth

5. A word people use to describe something unbelievable.

   In casual speech, hallucination is sometimes used to describe things that feel too strange or shocking to be true. It becomes a way to say, “I can’t believe what I just saw.”

   The party was so wild it felt like a hallucination.
   Seeing snow in summer felt like a hallucination.
   He said the concert experience was a total hallucination.

   Synonyms: unbelievable moment, shocking scene, unreal event, surreal experience, mind-blowing sight, impossible feeling, strange reality, dreamlike event, unbelievable sight, out-of-this-world moment, unreal scene, shocking experience
   Antonyms: ordinary moment, normal event, expected scene, predictable experience, usual sight, everyday reality, common occurrence, familiar feeling, plain experience, routine moment, standard situation, typical event