A linguist in the academic sense is a person who studies natural language (an academic discipline known as linguistics).
Ambiguously, the word is sometimes also used to refer to a polyglot (one who knows several languages), a translator/interpreter (especially in the military), or a grammarian (a scholar of grammar), but these uses of the word are distinct (and one does not have to be multilingual in order to be an academic linguist).
[1] The following is a list of notable academic linguists.
In the list the description should be like this: surname, forename (country, year of birth-year of death), main achievement