fellow (Noun) — A boy or man. ex. "there's a fellow at the door"
fellow (Noun) — A friend who is frequently in the company of another. ex. "drinking fellows"
fellow (Noun) — A person who is member of one's class or profession. ex. "he sent e-mail to his fellow hackers"
fellow (Noun) — One of a pair. ex. "one eye was blue but its fellow was brown"
fellow (Noun) — A member of a learned society. ex. "he was elected a fellow of the American Physiological Association"
fellow (Noun) — An informal form of address for a man. ex. "Say, fellow, what are you doing?"
fellow (Noun) — A man who is the lover of a girl or young woman. ex. "if I'd known he was her fellow I wouldn't have asked"
fellow (Noun) — An academic who is a member of a college.
fellow (Noun) — An academic having a grant for research or advanced study; someone having a fellowship.