To make something abnormal or to cause something to deviate from the normal or expected state.
From abnormal + -ise (British variant of -ize). The verb form means to alter something so that it becomes abnormal or atypical.
This is primarily British spelling—American English prefers 'abnormalize'—and the difference reveals how the -ise/-ize split happened: British English kept the French-influenced '-ise' while American English gradually shifted toward '-ize' as a universal suffix!
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