An image vivid enough to be a hallucination but recognized as unreal

Wiktionary Word definitions in Wiktionary
n. A brief but vivid visual or auditory experience that is recognised as being unreal

WordNet Word definitions in WordNet
n. an image vivid enough to be a hallucination but recognized as unreal

Wikipedia Word definitions in Wikipedia
A pseudohallucination is an involuntary sensory experience vivid enough to be regarded as a hallucination , but recognised by the patient not to be the result of external stimuli. Unlike normal hallucination, which occurs when one sees, hears, smells, tastes ...