An adviser to the court on some matter of law who is not a party to the case; usually someone who wants to influence the outcome of a lawsuit involving matters of wide public interest WordNet 3.0 & Open English WordNet

An amicus curiae is an individual or organization who is not a party to a legal case, but who is permitted to assist a court by offering information, expertise, or insight that has a bearing on the issues in the case. Wikipedia

A legal Latin phrase, literally translated as "friend of the court" Wikipedia Disambiguation

Phrase Wikidata

An independent lawyer, not retained by any party, whom the court has ordered to provide legal submissions regarding the matter in dispute; for example, to provide submissions regarding the situation of an unrepresented litigant or accused person. Wiktionary