The Collaborative International Dictionary of English v.0.48:

Labor \La"bor\ (l[=a]"b[~e]r), n. [OE. labour, OF. labour,
   laber, labur, F. labeur, L. labor; cf. Gr. lamba`nein to
   take, Skr. labh to get, seize.] [Written also labour.]
   1. Physical toil or bodily exertion, especially when
      fatiguing, irksome, or unavoidable, in distinction from
      sportive exercise; hard, muscular effort directed to some
      useful end, as agriculture, manufactures, and like;
      servile toil; exertion; work.
      [1913 Webster]

            God hath set
            Labor and rest, as day and night, to men
            Successive.                           --Milton.
      [1913 Webster]

   2. Intellectual exertion; mental effort; as, the labor of
      compiling a history.
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   3. That which requires hard work for its accomplishment; that
      which demands effort.
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            Being a labor of so great a difficulty, the exact
            performance thereof we may rather wish than look
            for.                                  --Hooker.
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   4. Travail; the pangs and efforts of childbirth.
      [1913 Webster]

            The queen's in labor,
            They say, in great extremity; and feared
            She'll with the labor end.            --Shak.
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   5. Any pang or distress. --Shak.
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   6. (Naut.) The pitching or tossing of a vessel which results
      in the straining of timbers and rigging.
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   7. [Sp.] A measure of land in Mexico and Texas, equivalent to
      an area of 1771/7 acres. --Bartlett.

   8. (Mining.) A stope or set of stopes. [Sp. Amer.]
      [Webster 1913 Suppl.]

   Syn: Work; toil; drudgery; task; exertion; effort; industry;
        painstaking. See Toll.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Labor \La"bor\, v. t. [F. labourer, L. laborare.]
   1. To work at; to work; to till; to cultivate by toil.
      [1913 Webster]

            The most excellent lands are lying fallow, or only
            labored by children.                  --W. Tooke.
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   2. To form or fabricate with toil, exertion, or care. "To
      labor arms for Troy." --Dryden.
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   3. To prosecute, or perfect, with effort; to urge
      strenuously; as, to labor a point or argument.
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   4. To belabor; to beat. [Obs.] --Dryden.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Labor \La"bor\, v. i. [imp. & p. p. Labored; p. pr. & vb. n.
   Laboring.] [OE. labouren, F. labourer, L. laborare. See
   Labor, n.] [Written also labour.]
   1. To exert muscular strength; to exert one's strength with
      painful effort, particularly in servile occupations; to
      work; to toil.
      [1913 Webster]

            Adam, well may we labor still to dress
            This garden.                          --Milton.
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   2. To exert one's powers of mind in the prosecution of any
      design; to strive; to take pains.
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   3. To be oppressed with difficulties or disease; to do one's
      work under conditions which make it especially hard,
      wearisome; to move slowly, as against opposition, or under
      a burden; to be burdened; -- often with under, and
      formerly with of.
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            The stone that labors up the hill.    --Granville.
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            The line too labors, and the words move slow.
                                                  --Pope.
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            To cure the disorder under which he labored. --Sir
                                                  W. Scott.
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            Come unto me, all ye that labor and are heavy laden,
            and I will give you rest.             --Matt. xi. 28
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   4. To be in travail; to suffer the pangs of childbirth; to be
      in labor.
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   5. (Naut.) To pitch or roll heavily, as a ship in a turbulent
      sea. --Totten.
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WordNet (r) 3.0 (2006):

labor
    n 1: a social class comprising those who do manual labor or work
         for wages; "there is a shortage of skilled labor in this
         field" [syn: labor, labour, working class,
         proletariat]
    2: productive work (especially physical work done for wages);
       "his labor did not require a great deal of skill" [syn:
       labor, labour, toil]
    3: concluding state of pregnancy; from the onset of contractions
       to the birth of a child; "she was in labor for six hours"
       [syn: parturiency, labor, labour, confinement,
       lying-in, travail, childbed]
    4: an organized attempt by workers to improve their status by
       united action (particularly via labor unions) or the leaders
       of this movement [syn: labor movement, trade union
       movement, labor]
    5: a political party formed in Great Britain in 1900;
       characterized by the promotion of labor's interests and
       formerly the socialization of key industries [syn: British
       Labour Party, Labour Party, Labour, Labor]
    6: the federal department responsible for promoting the working
       conditions of wage earners in the United States; created in
       1913 [syn: Department of Labor, Labor Department,
       Labor, DoL]
    7: any piece of work that is undertaken or attempted; "he
       prepared for great undertakings" [syn: undertaking,
       project, task, labor]
    v 1: strive and make an effort to reach a goal; "She tugged for
         years to make a decent living"; "We have to push a little
         to make the deadline!"; "She is driving away at her
         doctoral thesis" [syn: tug, labor, labour, push,
         drive]
    2: work hard; "She was digging away at her math homework";
       "Lexicographers drudge all day long" [syn: labor, labour,
       toil, fag, travail, grind, drudge, dig, moil]
    3: undergo the efforts of childbirth [syn: labor, labour]

Moby Thesaurus II by Grady Ward, 1.0:

206 Moby Thesaurus words for "labor":
   accouchement, activities, activity, affair, affairs, aim,
   always trot out, amplify, assignment, bag, be busy, be confined,
   be determined, be employed, bear, bear a child, bear young,
   belabor, birth, birth throes, birthing, blessed event, blunder,
   business, busywork, calve, careen, career, carry on business, cast,
   char, chare, charge, childbearing, childbed, childbirth, chore,
   commerce, commission, complete, concern, concernment, confinement,
   cultivate, delivery, detail, dirty work, do business, do chars,
   do the chores, donkeywork, dress, drive, drop, drudge, drudgery,
   duty, dwell on, dwell upon, effort, elaborate, employ, employees,
   employment, endeavor, endure, enlarge, enlarge upon,
   enter into detail, enterprise, errand, exercise, exertion, expand,
   fag, falter, farrow, fatigue, fawn, fish to fry, flounce, flounder,
   foal, follow a trade, function, genesis, give birth, giving birth,
   go into, grind, hammer away at, handiwork, handwork, hard work,
   harp on, hatching, have, have a baby, have a job, have young,
   having a baby, homework, industry, insist upon, interest, job,
   job of work, keep up, kitten, labor under, laborers, laboriousness,
   lamb, lick, lick of work, lie in, litter, lookout, lurch,
   make-work, manual labor, matter, matters in hand, mission, moil,
   moonlight, multiparity, nascency, nativity, occupation, odd job,
   overdo, overemphasize, overstress, pains, parturition,
   piece of work, pitch, pitch and plunge, plunge,
   practice a profession, project, pup, rat race, reel, resolve, rock,
   roll, scut work, seek, seethe, service, set up shop, slave,
   slavery, slogging, spadework, spell out, stagger, stay employed,
   stint, strain, strive, stroke, stroke of work, struggle, study,
   stumble, suffer, sway, sweat, sweat blood, swing, swot, task, tend,
   the Nativity, the stork, thing, things to do, thrash about,
   thresh over, throw, tiresome work, toil, toss, toss and tumble,
   toss and turn, totter, transact business, travail, treadmill, tug,
   tumble, turn a hand, undertaking, wallop, wallow, welter, whelp,
   work, work at, work for, work out, workers, yean



Bouvier's Law Dictionary, Revised 6th Ed (1856):

LABOR. Continued operation; work.
     2. The labor and skill of one man is frequently used in a partnership,
and valued as equal to the capital of another.
     3. When business has been done for another, and suit is brought to
recover a just reward, there is generally contained in the declaration, a
count for work and labor.
     4. Where penitentiaries exist, persons who have committed crimes are
condemned to be imprisoned therein at labor.



The Devil's Dictionary (1881-1906):

LABOR, n.  One of the processes by which A acquires property for B.