A post-mortem, also known as an autopsy, is the examination of a body after death. The aim of a post-mortem is to determine the cause of death. Definition of post-mortem noun in Oxford Advanced Learner's Dictionary. Meaning, pronunciation, picture, example sentences, grammar, usage notes, synonyms and more. Autopsy vs. Post-Mortem: A Comparative Analysis Autopsy and post-mortem are terms often used interchangeably, yet they hold distinct meanings within the fields of forensic science, medicine, and law. Both procedures involve examining a deceased body to determine the cause of death, but they differ in their scope, purpose, and context. POST MORTEM definition: 1. happening or taken after a person or animal dies: 2. a medical examination of a dead person's…. Learn more.