The Collaborative International Dictionary of English v.0.48:

Appease \Ap*pease"\, v. t. [imp. & p. p. Appealed; p. pr. &
   vb. n. Appeasing.] [OE. apesen, apaisen, OF. apaisier,
   apaissier, F. apaiser, fr. a (L. ad) + OF. pais peace, F.
   paix, fr. L. pax, pacis. See Peace.]
   To make quiet; to calm; to reduce to a state of peace; to
   still; to pacify; to dispel (anger or hatred); as, to appease
   the tumult of the ocean, or of the passions; to appease
   hunger or thirst.
   [1913 Webster]

   Syn: To pacify; quiet; conciliate; propitiate; assuage;
        compose; calm; allay; hush; soothe; tranquilize.
        [1913 Webster]

WordNet (r) 3.0 (2006):

appease
    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: overcome or allay; "quell my hunger" [syn: quell, stay,
       appease]
    3: make peace with [syn: propitiate, appease]

Moby Thesaurus II by Grady Ward, 1.0:

86 Moby Thesaurus words for "appease":
   abate, allay, alleviate, anesthetize, assuage, benumb, calm,
   calm down, cater to, coddle, compose, conciliate, content, cool,
   cradle, cushion, deaden, deaden the pain, defuse, diminish,
   dulcify, dull, ease, ease matters, even out, extenuate, feast,
   feed, foment, gentle, give relief, gloss over, gratify, hush,
   immolate before, lay, lay the dust, lessen, lull,
   make propitiation, make sacrifice to, mitigate, mollify, numb,
   offer sacrifice, pacify, pad, palliate, pamper, placate, poultice,
   pour balm into, pour balm on, pour oil on, propitiate, quell,
   quench, quiet, reduce, regale, relieve, rest, rock, rock to sleep,
   sacrifice, salve, sate, satiate, satisfy, slacken, slake, smooth,
   smooth down, smooth over, smoothen, soften, soothe, spoil,
   stabilize, steady, still, stupe, subdue, sweeten, tranquilize,
   whitewash