Definitions for "Concerted"
any musical composition that contrasts opposing timbres or performance forces; polychoral music; music involving spacial separation between instrumental / choral ensembles
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"
Mutually contrived or planned; agreed on; as, concerted schemes, signals.
Keywords:  arrows, happen, wise, once, step
Applied to a reaction mechanism, if it is concerted, all the arrows happen at once. See also Step-Wise.