The Collaborative International Dictionary of English v.0.48:

Assuage \As*suage"\, v. t. [imp. & p. p. Assuaged; p. pr. &
   vb. n. Assuaging.] [OE. asuagen, aswagen, OF. asoagier,
   asuagier, fr. assouagier, fr. L. ad + suavis sweet. See
   Sweet.]
   To soften, in a figurative sense; to allay, mitigate, ease,
   or lessen, as heat, pain, or grief; to appease or pacify, as
   passion or tumult; to satisfy, as appetite or desire.
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         Refreshing winds the summer's heat assuage. --Addison.
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         To assuage the sorrows of a desolate old man --Burke.
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         The fount at which the panting mind assuages
         Her thirst of knowledge.                 --Byron.
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   Syn: To alleviate; mitigate; appease; soothe; calm;
        tranquilize; relieve. See Alleviate.
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The Collaborative International Dictionary of English v.0.48:

Assuage \As*suage"\, v. i.
   To abate or subside. [Archaic] "The waters assuaged." --Gen.
   vii. 1.
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         The plague being come to a crisis, its fury began to
         assuage.                                 --De Foe.
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WordNet (r) 3.0 (2006):

assuage
    v 1: cause to be more favorably inclined; gain the good will of;
         "She managed to mollify the angry customer" [syn: pacify,
         lenify, conciliate, assuage, appease, mollify,
         placate, gentle, gruntle]
    2: satisfy (thirst); "The cold water quenched his thirst" [syn:
       quench, slake, allay, assuage]
    3: provide physical relief, as from pain; "This pill will
       relieve your headaches" [syn: relieve, alleviate,
       palliate, assuage]