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.
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            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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The Collaborative International Dictionary of English v.0.48:

Laboring \La"bor*ing\, a.
   1. That labors; performing labor; esp., performing coarse,
      heavy work, not requiring skill also, set apart for labor;
      as, laboring days.
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            The sleep of a laboring man is sweet. --Eccl. v. 12.
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   2. Suffering pain or grief. --Pope.
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   Laboring oar, the oar which requires most strength and
      exertion; often used figuratively; as, to have, or pull,
      the laboring oar in some difficult undertaking.
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WordNet (r) 3.0 (2006):

laboring
    adj 1: doing arduous or unpleasant work; "drudging peasants";
           "the bent backs of laboring slaves picking cotton";
           "toiling coal miners in the black deeps" [syn:
           drudging, laboring, labouring, toiling]