NOUN (1)

1. a performance of music by players or singers not involving theatrical staging;


VERB (2)

1. contrive (a plan) by mutual agreement;

2. settle by agreement;
- Example: "concert one's differences"

The Collaborative International Dictionary of English v.0.48:

Concert \Con*cert"\, v. t. [imp. & p. p. Concerted; p. pr. &
   vb. n. Concerting.] [F. concerter, It. concertare,
   conertare, prob. from L. consertus, p. p. of conserere to
   join together; con- + serere to join together, influenced by
   concertare to contend; con- + centare to strive; properly, to
   try to decide; fr. cernere to distinguish. See Series, and
   cf. Concern.]
   1. To plan together; to settle or adjust by conference,
      agreement, or consultation.
      [1913 Webster]

            It was concerted to begin the siege in March. --Bp.
                                                  Burnet.
      [1913 Webster]

   2. To plan; to devise; to arrange.
      [1913 Webster]

            A commander had more trouble to concert his defense
            before the people than to plan . . . the campaign.
                                                  --Burke.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Concert \Con*cert"\, v. i.
   To act in harmony or conjunction; to form combined plans.
   [1913 Webster]

         The ministers of Denmark were appointed to concert with
         Talbot.                                  --Bp. Burnet
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Concert \Con"cert\ (k[o^]n"s[~e]rt), n. [F. concert, It.
   concerto, conserto, fr. concertare. See Concert, v. t.]
   1. Agreement in a design or plan; union formed by mutual
      communication of opinions and views; accordance in a
      scheme; harmony; simultaneous action.
      [1913 Webster]

            All these discontents, how ruinous soever, have
            arisen from the want of a due communication and
            concert.                              --Swift.
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   2. Musical accordance or harmony; concord.
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            Let us in concert to the season sing. --Cowper.
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   3. A musical entertainment in which several voices or
      instruments take part.
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            Visit by night your lady's chamber window
            With some sweet concert.              --Shak.
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            And boding screech owls make the concert full.
                                                  --Shak.
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   Concert pitch. See under Pitch.
      [1913 Webster]

WordNet (r) 3.0 (2006):

concert
    n 1: a performance of music by players or singers not involving
         theatrical staging
    v 1: contrive (a plan) by mutual agreement
    2: settle by agreement; "concert one's differences"