The Collaborative International Dictionary of English v.0.48:

Commit \Com*mit"\, v. t. [imp. & p. p. Committed; p. pr. & vb.
   n. Committing.] [L. committere, commissum, to connect,
   commit; com- + mittere to send. See Mission.]
   1. To give in trust; to put into charge or keeping; to
      intrust; to consign; -- used with to, unto.
      [1913 Webster]

            Commit thy way unto the Lord.         --Ps. xxxvii.
                                                  5.
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            Bid him farewell, commit him to the grave. --Shak.
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   2. To put in charge of a jailor; to imprison.
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            These two were committed.             --Clarendon.
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   3. To do; to perpetrate, as a crime, sin, or fault.
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            Thou shalt not commit adultery.       --Ex. xx. 14.
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   4. To join for a contest; to match; -- followed by with. [R.]
      --Dr. H. More.
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   5. To pledge or bind; to compromise, expose, or endanger by
      some decisive act or preliminary step; -- often used
      reflexively; as, to commit one's self to a certain course.
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            You might have satisfied every duty of political
            friendship, without commiting the honor of your
            sovereign.                            --Junius.
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            Any sudden assent to the proposal . . . might
            possibly be considered as committing the faith of
            the United States.                    --Marshall.
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   6. To confound. [An obsolete Latinism.]
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            Committing short and long [quantities]. --Milton.
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   To commit a bill (Legislation), to refer or intrust it to a
      committee or others, to be considered and reported.

   To commit to memory, or To commit, to learn by heart; to
      memorize.

   Syn: To Commit, Intrust, Consign.

   Usage: These words have in common the idea of transferring
          from one's self to the care and custody of another.
          Commit is the widest term, and may express only the
          general idea of delivering into the charge of another;
          as, to commit a lawsuit to the care of an attorney; or
          it may have the special sense of intrusting with or
          without limitations, as to a superior power, or to a
          careful servant, or of consigning, as to writing or
          paper, to the flames, or to prison. To intrust denotes
          the act of committing to the exercise of confidence or
          trust; as, to intrust a friend with the care of a
          child, or with a secret. To consign is a more formal
          act, and regards the thing transferred as placed
          chiefly or wholly out of one's immediate control; as,
          to consign a pupil to the charge of his instructor; to
          consign goods to an agent for sale; to consign a work
          to the press.
          [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

committed \committed\ adj.
   1. Bound or obligated, as under a pledge to a particular
      cause, action, or attitude. Opposite of uncommitted.

   Note: [Narrower terms: bound up, involved, wrapped up;
         dedicated, devoted; pledged, sworn]
         [WordNet 1.5]

   2. Associated in an exclusive sexual relationship; also
      called attached. Opposite of unattached.

   Note: [Narrower terms: affianced, bespoken, betrothed,
         engaged, pledged, promised(predicate); married]
         [Also See: loving.]

   Syn: attached.
        [WordNet 1.5]

   3. Consigned involuntarily to custody, as in a prison or
      mental institution.
      [WordNet 1.5]

WordNet (r) 3.0 (2006):

committed
    adj 1: bound or obligated, as under a pledge to a particular
           cause, action, or attitude; "committed church members";
           "a committed Marxist" [ant: uncommitted]
    2: associated in an exclusive sexual relationship [syn:
       attached, committed] [ant: unattached, uncommitted]

Moby Thesaurus II by Grady Ward, 1.0:

111 Moby Thesaurus words for "committed":
   abandoned, affianced, afire, altruistic, ardent, assured, beholden,
   beholden to, betrothed, bound, bound and determined, bounden,
   bounden to, burning, compromised, consecrated, constant,
   contracted, decided, decisive, dedicated, definite, determined,
   devoted, devout, disinterested, duty-bound, earnest, engaged,
   faithful, fast, fervent, fervid, fiery, flaming, guaranteed,
   hearty, heated, hot, hot-blooded, humble, impassioned,
   in duty bound, in earnest, indebted to, intended, intense, intent,
   intent on, loyal, modest, obligate, obligated, obliged, obliged to,
   obstinate, on fire, passionate, perfervid, persevering, persistent,
   pledged, plighted, promised, purposeful, red-hot, relentless,
   resolute, resolved, sacrificing, saddled, self-abasing,
   self-abnegating, self-abnegatory, self-denying, self-devoted,
   self-effacing, self-forgetful, self-immolating, self-neglectful,
   self-neglecting, self-renouncing, self-sacrificing,
   self-unconscious, selfless, serious, sincere, single-minded,
   spirited, staunch, steadfast, sworn, tenacious, tested, tied,
   tried, tried and true, true, unacquisitive, under obligation,
   underwritten, unpossessive, unpretentious, unselfish,
   unsparing of self, vehement, warm, warranted, white-hot,
   wholehearted, zealous