nolle prosequi

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A declaration that the plaintiff in a civil case or the prosecutor in a criminal case will drop prosecution of all or part of a suit or indictment.

from The Century Dictionary.

• noun In law: in civil actions, an acknowledgment by the plaintiff that he will not further prosecute his suit, as to the whole or a part of the cause of action, or against some or one of several defendants (Bingham);
• noun in criminal cases, a declaration of record from the legal representative of the government that he will no further prosecute the particular indictment or some designated part thereof (Bishop). Abbreviated nol. pros.

from the GNU version of the Collaborative International Dictionary of English.

• (Law) Will not prosecute; -- an entry on the record, denoting that a plaintiff discontinues his suit, or the attorney for the public a prosecution; either wholly, or as to some count, or as to some of several defendants.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun law A declaration by the prosecutor that a civil or criminal prosecution will not proceed.
• noun figuratively A refusal, a denial, a rejection.
• verb law, transitive To issue such an declaration about a particular (charge or case).

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun an entry in the court record to the effect that the plaintiff or prosecutor will not proceed
• verb drop prosecution of by entering a nolle prosequi in the court records