Definition: Abnormal (noun) 1. abnormal: [ˌæbəˈneɪm ˈreɪndʒ] a deviation from normal or standard; abnormal in its nature, degree, quantity, etc. 2. abnormality: [ˈæbəˈnɪtʃəns] an aberrant condition, state, or quality 3. abnormality of something: [ˌæbˈniəm ˈhɜːrɪnt ] an abnormality in something that is not normal or expected to occur naturally. 4. abnormal (verb) a) To be out of proportion to normal standards, patterns, etc. b) To become abnormal or inappropriate. In psychology: • Abnormal states are those which are not in the natural state of being in a person’s psyche. • The term is also used to refer to abnormal mental activities like delusions and hallucinations in people with schizophrenia. In biology: • An abnormal organism may be an organism that differs significantly from normal organisms but does not change them.