Lewis & Short

dēfensĭo, ōnis, f. [defendo, no. II.], a defending, defence.

  1. I. Prop.: Remis cum spe defensionis studium propugnandi accessit, Caes. B. G. 2, 7, 2.
    With gen. subj.: urbium, id. ib. 7, 23, 5; id. B. C. 2, 7 fin.: ad istam omnem orationem brevis est defensio, Cic. Cael. 4; id. Verr. 2, 3, 88; id. Mil. 6, 15: nostra propugnatio ac defensio dignitatis tuae, id. Fam. 1, 7, 2 et saep.
    With gen. obj.: defensio criminis, Quint. 7, 4, 3: criminum, Liv. 38, 49, 6: sceleris, Just. 39, 2, 8.
    1. B. Concr., a written defence, speech: defensionem Demosthenes legit, Plin. 7, 30, 31, § 110.
  2. II. As jurid. t. t.
        1. a. The legal maintenance of a right: libertatis, Cod. Just. 1, 7, 18.
        2. b. (Acc. to defendo, no. II. B. 2.) Legal prosecution, punishment of a crime: mortis, Dig. 29, 5, 1, § 25.