The Collaborative International Dictionary of English v.0.48:

Spar \Spar\, v. i. [imp. & p. p. Sparred; p. pr. & vb. n.
   Sparring.] [Of uncertain origin; cf. OF. esparer to kick,
   F. ['e]parer, or Icel. sperra to stretch out the legs, to
   struggle.]
   1. To strike with the feet or spurs, as cocks do.
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   2. To use the fists and arms scientifically in attack or
      defense; to contend or combat with the fists, as for
      exercise or amusement; to box.
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            Made believe to spar at Paul with great science.
                                                  --Dickens.
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   3. To contest in words; to wrangle. [Colloq.]
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WordNet (r) 3.0 (2006):

sparring
    n 1: an argument in which the participants are trying to gain
         some advantage
    2: making the motions of attack and defense with the fists and
       arms; a part of training for a boxer [syn: spar,
       sparring]