The Collaborative International Dictionary of English v.0.48:

Slake \Slake\, v. t. [imp. & p. p. Slaked; p. pr. & vb. n.
   Slaking.] [OE. slaken to render slack, to slake, AS.
   sleacian, fr. sleac slack. See Slack, v. & a.]
   1. To allay; to quench; to extinguish; as, to slake thirst.
      "And slake the heavenly fire." --Spenser.
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            It could not slake mine ire nor ease my heart.
                                                  --Shak.
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   2. To mix with water, so that a true chemical combination
      shall take place; to slack; as, to slake lime.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Slake \Slake\, v. i.
   1. To go out; to become extinct. "His flame did slake." --Sir
      T. Browne.
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   2. To abate; to become less decided. [R.] --Shak.
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   3. To slacken; to become relaxed. "When the body's strongest
      sinews slake." [R.] --Sir J. Davies.
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   4. To become mixed with water, so that a true chemical
      combination takes place; as, the lime slakes.
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   Slake trough, a trough containing water in which a
      blacksmith cools a forging or tool.
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WordNet (r) 3.0 (2006):

slake
    v 1: satisfy (thirst); "The cold water quenched his thirst"
         [syn: quench, slake, allay, assuage]
    2: make less active or intense [syn: slake, abate, slack]
    3: cause to heat and crumble by treatment with water; "slack
       lime" [syn: slack, slake]

Moby Thesaurus II by Grady Ward, 1.0:

79 Moby Thesaurus words for "slake":
   abate, allay, alleviate, anesthetize, appease, assuage, bate,
   benumb, cloy, cram, cushion, deaden, deaden the pain, diminish,
   dull, ease, ease matters, ease off, ease up, engorge, feast, feed,
   fill, fill up, foment, fulfill, give relief, glut, gorge, gratify,
   jade, lay, lessen, let down, let up, loose, loosen, lull, mitigate,
   mollify, numb, overdose, overfeed, overfill, overgorge,
   oversaturate, overstuff, pad, pall, palliate, poultice,
   pour balm into, pour oil on, quench, reduce, regale, relax,
   relieve, remit, salve, sate, satiate, satisfy, saturate, slack,
   slack off, slack up, slacken, soften, soothe, stuff, stupe, subdue,
   supersaturate, surfeit, unbend, unbrace, unstrain, unstring