Definition of nonsuit:
(n) :
A lawsuit that is dismissed as having been brought without cause, prior to an adjudication on the merits.
(v) :
(transitive, law) To dismiss (a suit or plaintiff) on the grounds of his or her lawsuit having been brought without cause, prior to an adjudication on the merits.
(n) :
A neglect or failure by the plaintiff to follow up his suit; a renunciation or withdrawal of the cause by the plaintiff.