The Collaborative International Dictionary of English v.0.48:

Non pros \Non" pros.`\
   An abbreviation of Non prosequitur.
   [1913 Webster]

WordNet (r) 3.0 (2006):

non pros
    n 1: a judgment entered in favor of the defendant when the
         plaintiff has not continued his action (e.g., has not
         appeared in court) [syn: non prosequitur, non pros]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

NON PROS, or NON PROSEQUITUR. The name of a judgment rendered against a
plaintiff for neglecting to prosecute his suit agreeably to law and the
rules of the court. Vide Grah. Pr. 763; 3 Chit. Pr. 910; 1 Sell. Pr. 359; 1
Penna. Pr. 84; Caines' Pr. 102; 2 Arch. Pr. 204 and article Judgment of Non
Pros.