The noun fellow has 5 senses (first 3 from tagged texts)
1. (48) chap, fellow, feller, lad, gent, fella, blighter, cuss -- (a boy or man; "that chap is your host"; "there's a fellow at the door"; "he's a likable cuss")
2. (20) companion, comrade, fellow, familiar, associate -- (a person who is frequently in the company of another; "drinking companions"; "comrades in arms")
3. (18) colleague, confrere, fellow -- (a person who is member of your class or profession; "the surgeon consulted his colleagues"; "he sent e-mail to his fellow hackers")
4. fellow, dude, buster -- (an informal form of address for a man; "Say, fellow, what are you doing?"; "Hey buster, what's up?")
5. boyfriend, fellow, beau, swain, young man -- (a man who is the lover of a girl or young woman; "if I'd known he was her boyfriend I wouldn't have asked")