Expert/ˈekspɜːrt/ Definition 1 of 4Pro Tip 1/2Subject Specific Use 'expert' when referring to a person's deep understanding of a particular topic. A chess expert can anticipate moves many turns ahead. Pro Tip 2/2Not a Beginner 'Expert' implies a high level of proficiency, more than just a hobbyist or amateur. Only an expert in linguistics can decipher this manuscript.