The Collaborative International Dictionary of English v.0.48:

Non-pros \Non`-pros"\, v. t. [imp. & p. p. Nonprossed; p. pr.
   & vb. n. Non-prossing.]
   To decline or fail to prosecute; to allow to be dropped (said
   of a suit); to enter judgment against (a plaintiff who fails
   to prosecute); as, the plaintiff was non-prossed.
   [1913 Webster]