Definitions from Black's Law Dictionary: 2nd Edition and Ballentine's Law Dictionary as are available for each term in each dictionary.
  • Ballentine's Law Dictionary

    Of mere motion.

  • Black's Law Dictionary: 2nd Edition

    Of his own mere motion; of his own accord; voluntarily and without prompting or request. Royal letters patent which are granted at the crown's own instance, and without request made, are said to be granted ex mero motu. When a court interferes, of its own motion, to object to an irregularity, or to do something which the parties are not strictly entitled to, but which will prevent injustice, it is said to act ex mero motu, or ex proprio motu, or sua sponte, all these terms bsing here equivalent.