The Collaborative International Dictionary of English v.0.48:

Nolo contendere \No"lo con*ten"de*re\ [L., I do not wish to
   contend.] (Law)
   A plea, by the defendant, in a criminal prosecution, which,
   without admitting guilt, subjects him to all the consequences
   of a plea of guilty.
   [1913 Webster]

WordNet (r) 3.0 (2006):

nolo contendere
    n 1: (law) an answer of `no contest' by a defendant who does not
         admit guilt but that subjects him to conviction [syn: nolo
         contendere, non vult]