From Longman Business Dictionary
copywritercop·y·writ·er /ˈkɒpiˌraɪtəˈkɑːpiˌraɪtər/ noun [countableC] MARKETINGJOBsomeone whose job is to write COPY (=written material) for advertisementsMost brand managers or copywriters in advertising agencies are under the age of 40.