The Collaborative International Dictionary of English v.0.48:

Acquaint \Ac*quaint"\, v. t. [imp. & p. p. Acquainted; p. pr.
   & vb. n. Acquainting.] [OE. aqueinten, acointen, OF.
   acointier, LL. adcognitare, fr. L. ad + cognitus, p. p. of
   cognoscere to know; con- + noscere to know. See Quaint,
   Know.]
   1. To furnish or give experimental knowledge of; to make
      (one) to know; to make familiar; -- followed by with.
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            Before a man can speak on any subject, it is
            necessary to be acquainted with it.   --Locke.
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            A man of sorrows and acquainted with grief. --Isa.
                                                  liii. 3.
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   2. To communicate notice to; to inform; to make cognizant; --
      followed by with (formerly, also, by of), or by that,
      introducing the intelligence; as, to acquaint a friend
      with the particulars of an act.
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            Acquaint her here of my son Paris' love. --Shak.
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            I must acquaint you that I have received
            New dated letters from Northumberland. --Shak.
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   3. To familiarize; to accustom. [Obs.] --Evelyn.
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   To be acquainted with, to be possessed of personal
      knowledge of; to be cognizant of; to be more or less
      familiar with; to be on terms of social intercourse with.
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   Syn: To inform; apprise; communicate; advise.
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The Collaborative International Dictionary of English v.0.48:

Acquainted \Ac*quaint"ed\, a.
   Personally known; familiar. See To be acquainted with,
   under Acquaint, v. t.
   [1913 Webster]

WordNet (r) 3.0 (2006):

acquainted
    adj 1: having fair knowledge of; "they were acquainted"; "fully
           acquainted with the facts"