To adopt an exaggerated or affected attitude or pose; to strike attitudes or assume artificial positions.
From attitude + -ise (British English verb suffix). This verb emerged in the late 17th-18th centuries as a critical term to describe people who were constantly posing or affecting attitudes.
British English created this verb to describe what we'd now call 'being extra' or 'being dramatic.' It specifically means pretending your feelings or positions are bigger and more important than they really are.
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