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.
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