Lewis & Short

dēscensĭo, ōnis, f. [descendo] (postAug.), a going down, descending.

  1. I. Prop.: balinearum, into the bath, Plin. 20, 17, 69, § 178: Tiberina, the sail down the Tiber, Cic. Fin. 5, 24, 70: grando in descensione saltus, upon the thickets, Vulg. Isa. 32, 19.
    Hence,
  2. * II. Meton., the bath itself, Gr. ἐμβάσεις, Plin. Ep. 5, 6, 26.