Source : Webster's Revised Unabridged Dictionary (1913)

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.

            It was concerted to begin the siege in March. --Bp.
                                                  Burnet.

   2. To plan; to devise; to arrange.

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

Concerted \Con*cert"ed\, a.
   Mutually contrived or planned; agreed on; as, concerted
   schemes, signals.

   {Concerted piece} (Mus.), a composition in parts for several
      voices or instrument, as a trio, a quartet, etc.

Source : WordNet®

concerted
     adj : involving the joint activity of two or more; "the attack was
           met by the combined strength of two divisions";
           "concerted action"; "the conjunct influence of fire and
           strong dring"; "the conjunctive focus of political
           opposition"; "a cooperative effort"; "a united effort";
           "joint military activities" [syn: {combined}, {conjunct},
            {conjunctive}, {cooperative}, {united}]