The Collaborative International Dictionary of English v.0.48:

Slavery \Slav"er*y\, n.; pl. Slaveries. [See 2d Slave.]
   1. The condition of a slave; the state of entire subjection
      of one person to the will of another.
      [1913 Webster]

            Disguise thyself as thou wilt, still, slavery, said
            I, still thou art a bitter draught!   --Sterne.
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            I wish, from my soul, that the legislature of this
            state [Virginia] could see the policy of a gradual
            abolition of slavery. It might prevent much future
            mischief.                             --Washington.
      [1913 Webster]

   2. A condition of subjection or submission characterized by
      lack of freedom of action or of will.
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            The vulgar slaveries rich men submit to. --C. Lever.
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            There is a slavery that no legislation can abolish,
            -- the slavery of caste.              --G. W. Cable.
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   3. The holding of slaves.
      [1913 Webster]

   Syn: Bondage; servitude; inthrallment; enslavement;
        captivity; bond service; vassalage.
        [1913 Webster]

WordNet (r) 3.0 (2006):

slavery
    n 1: the state of being under the control of another person
         [syn: bondage, slavery, thrall, thralldom,
         thraldom]
    2: the practice of owning slaves [syn: slavery,
       slaveholding]
    3: work done under harsh conditions for little or no pay

Moby Thesaurus II by Grady Ward, 1.0:

77 Moby Thesaurus words for "slavery":
   abjectness, absolutism, attendance, baseness, bond service,
   bondage, captivity, control, debt slavery, deprivation of freedom,
   dirty work, disenfranchisement, disfranchisement, domination,
   donkeywork, drudge, drudgery, employ, employment, enslavement,
   enthrallment, fag, fatigue, feudalism, feudality, grind, handiwork,
   handwork, hard labor, helotism, helotry, indentureship, industry,
   labor, lick, lick of work, manual labor, meanness, menialness,
   ministration, ministry, moil, peonage, plugging, rat race,
   restraint, scut work, serfdom, serfhood, servility, servitium,
   servitorship, servitude, slavishness, spadework, strain, stroke,
   stroke of work, subjection, subjugation, submissiveness,
   subservience, subserviency, sweat, task, tendance, thrall,
   thralldom, tiresome work, toil, travail, treadmill, tyranny,
   vassalage, villenage, work, yoke



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

SLAVERY. The state or condition of a slave.
     2. Slavery exists in most of the southern states. In Pennsylvania, by
the act of March, 1780, for the gradual abolition of slavery, it has been
almost entirely removed in Massachusetts it was held, soon after the
Revolution, that slavery had been abolished by their constitution; 4 Mass.
128; in Connecticut, slavery has been totally extinguished by legislative
provisions; Reeve's Dom. Bel. 340; the states north of Delaware, Maryland
and the river Ohio, may be considered as free States, where slavery is not
tolerated. Vide Stroud on Slavery; 2 Kent, Com. 201; Rutherf. Inst. 238.