Oxford Dictionary English first mate nounnoun BrE BrE//ˌfɜːst ˈmeɪt// ; NAmE NAmE//ˌfɜːrst ˈmeɪt// (also first officer) People in sea travel Add to my wordlistjump to other results the officer on a commercial ship just below the rank of captain or master See related entries: People in sea travelSee first mate in the Oxford Advanced American DictionaryCheck pronunciation: first mate oxfordlearnersdictionaries.com