Ad Litem Definition: Latin: for the suit. Related Terms: Guardian Ad Litem, Litigation An individual appointed only for the purposes of prosecuting or defending a court action or litigation, on behalf of a vulnerable or otherwise undefended interest (such as a child or mentally-challenged person). In Latin Words and Phrases for Lawyers: "For the purpose of the suit. Thus in a suit against the estate of a deceased person where no letters of administration or probate have been taken out, the court may appoint an administrator ad litem to protect the interests of the estate." REFERENCES: Sodhi, D., Latin Words & Phrases for Lawyers (New York: Law and Business Publications inc., 1980), page 23. Categories & Topics: Dictionary of Latin Law Terms Family Law Dictionary Trusts, Wills, Estates and Probate Law Dictionary Find you are constantly looking up definitions? Try our search provider (works in most modern browsers) If you find an error or omission in Duhaime's Legal Dictionary, or if you have legal term suggestion, we'd love to hear from you!