The Collaborative International Dictionary of English v.0.48:

Contestation \Con`tes*ta"tion\, n. [L. contestatio testimony:
   cf. F. contestation a contesting.]
   1. The act of contesting; emulation; rivalry; strife;
      dispute. "Loverlike contestation." --Milton.
      [1913 Webster]

            After years spent in domestic, unsociable
            contestations, she found means to withdraw.
                                                  --Clarendon.
      [1913 Webster]

   2. Proof by witness; attestation; testimony. [Obs.]
      [1913 Webster]

            A solemn contestation ratified on the part of God.
                                                  --Barrow.
      [1913 Webster]

WordNet (r) 3.0 (2006):

contestation
    n 1: a contentious speech act; a dispute where there is strong
         disagreement; "they were involved in a violent argument"
         [syn: controversy, contention, contestation,
         disputation, disceptation, tilt, argument,
         arguing]