IPA: /ˈkɒpiˌriːdə/
KK: /ˈkɑːpiˌriːdər/
A person who checks and corrects written material, especially for newspapers or magazines, to ensure it is clear and free of errors before it is published.
The copyreader found several mistakes in the article before it went to print.
Copyreader → It is formed from "copy" (from Middle English *copie*, meaning a reproduction or duplicate) and "reader" (from Old English *rædere*, meaning one who reads). A copyreader is someone who reads and checks written material for errors before publication.
Think of someone who reads a 'copy' of a text to check for mistakes — that's what a copyreader does.