The Collaborative International Dictionary of English v.0.48:

Couple \Cou"ple\ (k[u^]p"'l), n. [F. couple, fr. L. copula a
   bond, band; co- + apere, aptum, to join. See Art, a., and
   cf. Copula.]
   1. That which joins or links two things together; a bond or
      tie; a coupler. [Obs.]
      [1913 Webster]

            It is in some sort with friends as it is with dogs
            in couples; they should be of the same size and
            humor.                                --L'Estrange.
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            I'll go in couples with her.          --Shak.
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   2. Two of the same kind connected or considered together; a
      pair; a brace. "A couple of shepherds." --Sir P. Sidney.
      "A couple of drops" --Addison. "A couple of miles."
      --Dickens. "A couple of weeks." --Carlyle.
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            Adding one to one we have the complex idea of a
            couple.                               --Locke.
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            [Ziba] met him with a couple of asses saddled. --2
                                                  Sam. xvi. 1.
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   3. A male and female associated together; esp., a man and
      woman who are married or betrothed.
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            Such were our couple, man and wife.   --Lloyd.
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            Fair couple linked in happy, nuptial league.
                                                  --Milton.
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   4. (Arch.) See Couple-close.
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   5. (Elec.) One of the pairs of plates of two metals which
      compose a voltaic battery; -- called a voltaic couple or
      galvanic couple.
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   6. (Mech.) Two rotations, movements, etc., which are equal in
      amount but opposite in direction, and acting along
      parallel lines or around parallel axes.
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   Note: The effect of a couple of forces is to produce a
         rotation. A couple of rotations is equivalent to a
         motion of translation.
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The Collaborative International Dictionary of English v.0.48:

Couple \Cou"ple\, v. t. [imp. & p. p. Coupled (k[u^]p"'ld); p.
   pr. & vb. n. Coupling (k[u^]p"l[i^]ng).] [F. coupler, fr.
   L. copulare. See Couple, n., and cf. Copulate, Cobble,
   v.]
   [1913 Webster]
   1. To link or tie, as one thing to another; to connect or
      fasten together; to join.
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            Huntsman, I charge thee, tender well my hounds, . .
            .
            And couple Clowder with the deep-mouthed brach.
                                                  --Shak.
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   2. To join in wedlock; to marry. [Colloq.]
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            A parson who couples all our beggars. --Swift.
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The Collaborative International Dictionary of English v.0.48:

Couple \Cou"ple\, v. i.
   To come together as male and female; to copulate. [Obs.]
   --Milton. Bacon.
   [1913 Webster]

WordNet (r) 3.0 (2006):

couple
    n 1: a pair who associate with one another; "the engaged
         couple"; "an inseparable twosome" [syn: couple,
         twosome, duo, duet]
    2: a pair of people who live together; "a married couple from
       Chicago" [syn: couple, mates, match]
    3: a small indefinite number; "he's coming for a couple of days"
    4: two items of the same kind [syn: couple, pair, twosome,
       twain, brace, span, yoke, couplet, distich,
       duo, duet, dyad, duad]
    5: (physics) something joined by two equal and opposite forces
       that act along parallel lines
    v 1: bring two objects, ideas, or people together; "This fact is
         coupled to the other one"; "Matchmaker, can you match my
         daughter with a nice young man?"; "The student was paired
         with a partner for collaboration on the project" [syn:
         match, mate, couple, pair, twin]
    2: link together; "can we couple these proposals?" [syn:
       couple, couple on, couple up] [ant: decouple,
       uncouple]
    3: form a pair or pairs; "The two old friends paired off" [syn:
       pair, pair off, partner off, couple]
    4: engage in sexual intercourse; "Birds mate in the Spring"
       [syn: copulate, mate, pair, couple]