Lewis & Short

transactĭo, ōnis, f. [transigo] (postclass.).

  1. I. A completing, completion: mundi, Tert. Anim. 55 med.: vitae, Ennod. Ep. 1, 6.
  2. II. In jurid. Lat., an agreement, transaction: de transactionibus, Dig. 2, tit. 15; 50, 16, 230.