insane

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US /ɪnˈseɪn/ 
UK /ɪnˈseɪn/ 

Longman Dictionary of Contemporary English

insane

insane /ɪnˈseɪn/ adjective
1. informal completely stupid or crazy, often in a way that is dangerous:
That’s an insane risk.
The whole idea sounds absolutely insane to me.
Why did you do that? Have you gone insane?
2. someone who is insane is permanently and seriously mentally ill so that they cannot live in normal society:
The killer was declared criminally insane.
3. the insane people who are mentally ill:
a hospital for the insane
4. drive somebody insane informal to make someone feel more and more annoyed or angry, usually over a long period of time SYN drive somebody mad:
My little brother’s been driving me insane all weekend.
—insanely adverb:
insanely jealous
She giggled insanely.

Oxford Advanced Learner's Dictionary

insane

in·sane   [ɪnˈseɪn] [ɪnˈseɪn] adjective

1. seriously mentally ill and unable to live in normal society

• Doctors certified him as insane. 

• The prisoners were slowly going insane. 

Opp:  sane

2. the insane noun plural people who are insane 

• a hospital for the insane 

3. (informal) very stupid, crazy or dangerous

• I must have been insane to agree to the idea. 

• This job is driving me insane (= making me feel very angry). 

see also  insanity

Derived Word: insanely 
 

Word Origin:

[insane insanely] mid 16th cent.: from Latin insanus, from in- ‘not’ + sanus ‘healthy’. 
 

Synonyms:

mentally ill

insane • neurotic • psychotic • disturbed • unstable 

These words all describe sb who is suffering from a mental illness.

mentally ill • suffering from an illness of the mind, especially in a way that affects the way you think and behave

insane • [not usually before noun] (rather formal) suffering from a serious mental illness and unable to live in normal society: ▪ The question is, was the man insane when he committed the crime? 

In informal English insane can describe sb who is not suffering from a mental illness, but whose mind does not work normally, especially because they are under pressure. This meaning is used especially in the phrases go insane and drive sb insane.

neurotic • (medical) suffering from or connected with neurosis (= a mental illness in which a person suffers strong feelings of fear and worry): ▪ the treatment of anxiety in neurotic patients 

In informal English neurotic is also used to describe sb who is not suffering from a mental illness, but is not behaving in a calm way because they are worried about sth: ▪ She became neurotic about keeping the house clean. 

psychotic • (medical) suffering from or connected with psychosis (= a serious mental illness in which thought and emotions lose connection with external reality). In informal English psychotic is sometimes used to describe anyone suffering from a mental illness, but in correct medical usage it only describes people who have difficulty relating to external reality. It contrasts with neurotic which describes people who are less seriously mentally ill and are still able to distinguish what is real from what is not.

disturbed • mentally ill, especially because of very unhappy or shocking experiences: ▪ He works with emotionally disturbed children. 

unstable • having emotions and behaviour that are likely to change suddenly and unexpectedly

neurotic/psychotic/disturbed/unstable behaviour 

neurotic/psychotic illnesses/disorders/symptoms/patients 

seriously mentally ill/neurotic/psychotic/disturbed

emotionally/mentally disturbed/unstable 
 

Example Bank:

• He is criminally insane, unable to stop himself attacking women. 

• He later became insane and was confined to an asylum. 

• He was clearly insane. 

• He went almost insane when he heard that his daughter had died. 

• In 1975 she was certified clinically insane and sent to a mental hospital. 

• It seems insane to cut the budget now. 

• She claimed she was temporarily insane during the attack. 

• The whole idea is quite insane. 

• You're driving me nearly insane with that noise. 

• Doctors certified her as insane. 

• It was an insane risk to take. 

• She was driving me insane with her constant chatter. 

• The question is, was the man insane when he committed the crime?

Cambridge Advanced Learner's Dictionary

Cambridge Advanced Learner's Dictionary - 4th Edition

insane / ɪnˈseɪn / adjective

C2 mentally ill:

For the last ten years of his life he was clinically insane.

informal I sometimes think I'm going insane (= I feel very confused) .

C1 extremely unreasonable or stupid:

It would be insane not to take advantage of this opportunity.

 

insane / ɪnˈseɪn / noun [ plural ]

the insane

mentally ill people:

a hospital for the criminally insane

© Cambridge University Press 2013