father-out-law noun3 •The father of one's boyfriend or girlfriend. •The father of any of one's friends. •The father of one's ex-spouse.One day, in an argument with his wife, Haydar, he made a terrible mistake. He refused to acknowledge Henock Beamare as his father-in-law. Instead, he referred to him as his father-out-law. — 2013 formsfathers-out-law
