The Collaborative International Dictionary of English v.0.48:

Prosecution \Pros`e*cu"tion\, n. [L. prosecutio a following.]
   1. The act or process of prosecuting, or of endeavoring to
      gain or accomplish something; pursuit by efforts of body
      or mind; as, the prosecution of a scheme, plan, design, or
      undertaking; the prosecution of war.
      [1913 Webster]

            Keeping a sharp eye on her domestics . . . in
            prosecution of their various duties.  --Sir W.
                                                  Scott.
      [1913 Webster]

   2. (Law)
      (a) The institution and carrying on of a suit in a court
          of law or equity, to obtain some right, or to redress
          and punish some wrong; the carrying on of a judicial
          proceeding in behalf of a complaining party, as
          distinguished from defense.
      (b) The institution, or commencement, and continuance of a
          criminal suit; the process of exhibiting formal
          charges against an offender before a legal tribunal,
          and pursuing them to final judgment on behalf of the
          state or government, as by indictment or information.
      (c) The party by whom criminal proceedings are instituted.
          --Blackstone. Burrill. Mozley & W.
          [1913 Webster]

WordNet (r) 3.0 (2006):

prosecution
    n 1: the institution and conduct of legal proceedings against a
         defendant for criminal behavior [syn: prosecution,
         criminal prosecution] [ant: defence, defense,
         demurrer, denial]
    2: the lawyers acting for the state to put the case against the
       defendant [ant: defence, defense, defense lawyers,
       defense team]
    3: the continuance of something begun with a view to its
       completion [syn: pursuance, prosecution]