The Collaborative International Dictionary of English v.0.48:

Acquiesce \Ac`qui*esce"\, v. i. [imp. & p. p. Acquiesced; p.
   pr. & vb. n. Acquiescing] [L. acquiescere; ad + quiescere
   to be quiet, fr. quies rest: cf. F. acquiescer. See Quiet.]
   1. To rest satisfied, or apparently satisfied, or to rest
      without opposition and discontent (usually implying
      previous opposition or discontent); to accept or consent
      by silence or by omitting to object; -- followed by in,
      formerly also by with and to.
      [1913 Webster]

            They were compelled to acquiesce in a government
            which they did not regard as just.    --De Quincey.
      [1913 Webster]

   2. To concur upon conviction; as, to acquiesce in an opinion;
      to assent to; usually, to concur, not heartily but so far
      as to forbear opposition.
      [1913 Webster]

   Syn: To submit; comply; yield; assent; agree; consent;
        accede; concur; conform; accept tacitly.
        [1913 Webster]

WordNet (r) 3.0 (2006):

acquiesce
    v 1: to agree or express agreement; "The Maestro assented to the
         request for an encore" [syn: assent, accede,
         acquiesce] [ant: dissent]

Moby Thesaurus II by Grady Ward, 1.0:

76 Moby Thesaurus words for "acquiesce":
   abide by, accede, accept, acclaim, accommodate, acquiesce in,
   adapt, adjust, agree, agree to, agree with, applaud, assent,
   be agreeable, be agreeable to, be dying to, be eager, be game,
   be open to, be persuaded, be ready, be spoiling for, be willing,
   bow, buy, cheer, coincide, collaborate, come around, come over,
   come round, come to, comply, comply with, concur, consent,
   cooperate, face the music, fall in with, give the nod,
   go along with, hail, hold with, in toto, incline, knock under,
   knuckle down, knuckle under, lean, live with it, look kindly upon,
   nod, nod assent, not hesitate to, not resist, obey, plunge into,
   receive, reconcile, relent, resign, submit, subscribe,
   subscribe to, succumb, swallow it, swallow the pill, take, take it,
   take kindly to, vote for, welcome, would as leave, would as lief,
   yes, yield assent