The Collaborative International Dictionary of English v.0.48:

Fellow \Fel"low\, n. [OE. felawe, felaghe, Icel. f[=e]lagi, fr.
   f[=e]lag companionship, prop., a laying together of property;
   f[=e] property + lag a laying, pl. l["o]g law, akin to liggja
   to lie. See Fee, and Law, Lie to be low.]
   1. A companion; a comrade; an associate; a partner; a sharer.
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            The fellows of his crime.             --Milton.
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            We are fellows still,
            Serving alike in sorrow.              --Shak.
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            That enormous engine was flanked by two fellows
            almost of equal magnitude.            --Gibbon.
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   Note: Commonly used of men, but sometimes of women. --Judges
         xi. 37.
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   2. A man without good breeding or worth; an ignoble or mean
      man.
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            Worth makes the man, and want of it, the fellow.
                                                  --Pope.
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   3. An equal in power, rank, character, etc.
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            It is impossible that ever Rome
            Should breed thy fellow.              --Shak.
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   4. One of a pair, or of two things used together or suited to
      each other; a mate; the male.
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            When they be but heifers of one year, . . . they are
            let go to the fellow and breed.       --Holland.
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            This was my glove; here is the fellow of it. --Shak.
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   5. A person; an individual.
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            She seemed to be a good sort of fellow. --Dickens.
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   6. In the English universities, a scholar who is appointed to
      a foundation called a fellowship, which gives a title to
      certain perquisites and privileges.
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   7. In an American college or university, a member of the
      corporation which manages its business interests; also, a
      graduate appointed to a fellowship, who receives the
      income of the foundation.
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   8. A member of a literary or scientific society; as, a Fellow
      of the Royal Society.
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   Note: Fellow is often used in compound words, or adjectively,
         signifying associate, companion, or sometimes equal.
         Usually, such compounds or phrases are
         self-explanatory; as, fellow-citizen, or fellow
         citizen; fellow-student, or fellow student;
         fellow-workman, or fellow workman; fellow-mortal, or
         fellow mortal; fellow-sufferer; bedfellow; playfellow;
         workfellow.
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               Were the great duke himself here, and would lift
               up
               My head to fellow pomp amongst his nobles.
                                                  --Ford.
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The Collaborative International Dictionary of English v.0.48:

Fellow \Fel"low\, v. t.
   To suit with; to pair with; to match. [Obs.] --Shak.
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WordNet (r) 3.0 (2006):

fellow
    n 1: a boy or man; "that chap is your host"; "there's a fellow
         at the door"; "he's a likable cuss"; "he's a good bloke"
         [syn: chap, fellow, feller, fella, lad, gent,
         blighter, cuss, bloke]
    2: a friend who is frequently in the company of another;
       "drinking companions"; "comrades in arms" [syn: companion,
       comrade, fellow, familiar, associate]
    3: a person who is member of one's class or profession; "the
       surgeon consulted his colleagues"; "he sent e-mail to his
       fellow hackers" [syn: colleague, confrere, fellow]
    4: one of a pair; "he lost the mate to his shoe"; "one eye was
       blue but its fellow was brown" [syn: mate, fellow]
    5: a member of a learned society; "he was elected a fellow of
       the American Physiological Association"
    6: an informal form of address for a man; "Say, fellow, what are
       you doing?"; "Hey buster, what's up?" [syn: fellow, dude,
       buster]
    7: 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" [syn:
       boyfriend, fellow, beau, swain, young man]