complaint

n. finding fault, act of expressing displeasure; pleading entered by a plaintiff (Law)

In general use, a complaint is an expression of displeasure, such as poor service at a store, or from a local government, etc. Under common law, a complaint is a formal legal document that sets out the basic facts and legal reasons (see: cause of action) that the filing party (the plaintiffs) believes are sufficient to support a claim against another person, persons, entity or entities (the defendants) that entitles the plaintiff(s) to a remedy (either money damages or injunctive relief). For example, the Federal Rules of Civil Procedure that govern civil litigation in United States courts provide that a civil action is commenced with the filing or service of a pleading called a complaint. Civil court rules in states that have incorporated the Federal Rules of Civil Procedure use the same term for the same pleading.
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(n.)
Expression of grief, regret, pain, censure, or resentment; lamentation; murmuring; accusation; fault-finding.
  

(n.)
Cause or subject of complaint or murmuring.
  

(n.)
An ailment or disease of the body.
  

(n.)
A formal allegation or charge against a party made or presented to the appropriate court or officer, as for a wrong done or a crime committed (in the latter case, generally under oath); an information; accusation; the initial bill in proceedings in equity.
  

(See Grievance.)

EU citizenship confers the right of complaint to the EU Ombudsman on matters to do with flawed administration by certain EU institutions. (See EU citizenship: Petition and Ombudsman, The European Ombudsman website)