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.
      [1913 Webster]

            It could not slake mine ire nor ease my heart.
                                                  --Shak.
      [1913 Webster]

   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.
      [1913 Webster]

   2. To abate; to become less decided. [R.] --Shak.
      [1913 Webster]

   3. To slacken; to become relaxed. "When the body's strongest
      sinews slake." [R.] --Sir J. Davies.
      [1913 Webster]

   4. To become mixed with water, so that a true chemical
      combination takes place; as, the lime slakes.
      [1913 Webster]

   Slake trough, a trough containing water in which a
      blacksmith cools a forging or tool.
      [1913 Webster]

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]