psychosis

n. severe mental disorder including delusions and loss of contact with reality

Psychosis is a generic psychiatric term for a mental state often described as involving a "loss of contact with reality". Stedman's Medical Dictionary defines psychosis as "a severe mental disorder, with or without organic damage, characterized by derangement of personality and loss of contact with reality and causing deterioration of normal social functioning."
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Psychosis is a symptom or feature of mental illness typically characterized by radical changes in personality, impaired [more]Psychosis - Community and Resources

Noun
1. any severe mental disorder in which contact with reality is lost or highly distorted
(hypernym) mental illness, mental disease, psychopathy
(hyponym) delirium tremens, DTs

(n.)
Any vital action or activity.
  

(n.)
A disease of the mind; especially, a functional mental disorder, that is, one unattended with evident organic changes.