Lewis & Short

2. prōcĭdentĭa, ae, f. [1. procido],

  1. I. a falling down or forwards of a part of the body out of its place, a procidence, prolapse: ani, Cels. 6, 6, 8 fin.: vulvarum, Plin. 23, 9, 81, § 161: sedis, id. 26, 8, 58, § 90; cf. procido, P. a.
  2. II. Gram. t. t. = ἀντίπτωσις, the substitution of one case for another, Prisc. 1099 P.