An amicus curiae is a party not directly involved in a case that may provide information or evidence to the court to help clear up a matter of law or inform the court of their position on the matter. In Latin amicus curiae means “a friend of the court.”
Merriam-Webster Online Dictionary
amicus curiae (noun) one (as a professional person or organization) that is not a party to a particular litigation but that is permitted by the court to advise it in respect to some matter of law that directly affects the case in question
Synonyms:
friend of the court