American Civil Liberties Union Legal Meaning and Definition

Here is a simplified definition of the legal term American Civil Liberties Union.

American Civil Liberties Union (noun): A nonprofit organization that works to protect and preserve the individual rights and liberties in the United States as secured by the Constitution and laws. The organization provides legal assistance in cases where it considers civil liberties to be threatened. Please note, this term is not related to the concept of arrears (unpaid, overdue debts) mentioned in the example you've given.