Latin for "of one's own accord; voluntarily." Used to indicate that a court has taken notice of an issue on its own motion without prompting or suggestion from either party.
As a general rule, where grounds for dismissal exist, an action is subject to dismissal on a court's own motion. A trial court has the power to dismiss an action sua sponte for want of prosecution, or failure to comply with the rules of civil procedure or a court's orders. A court may sua sponte enter a motion to dismiss for want of jurisdiction even though both parties have agreed to appear in the court.
See, e.g., Carlisle v. United States, 517 US 416 (1996) and Trest v. Cain, 522 US 87 (1997).