Lewis & Short

contestātĭo, ōnis, f. [contestor].

  1. I. A jurid. t. t., an attesting, proving by witness, testimony: suprema testamenti, Dig. 28, 1, 20, § 8; cf.: verbum (testamentum) compositum a mentis contestatione, Gell. 6, 12, 2: litis, a formal entering of a suit in law, by calling witnesses, Gai inst. 3, 180 sq.; Dig. 3, 3, 40, § 3; 24, 3, 22, § 5; Cod. Just. 3, 9: de litis contestatione.
    1. B. Out of the circle of judicial proceedings, attestation, conclusive proof: in tam miserā atque maestā publicae injuriae contestatione, Gell. 10, 3, 4.
  2. * II. An earnest entreaty: petivit tamen a me pater maximā contestatione, ut, etc., * Cic. Corn. 1 Fragm. 5 B. and K.