Lewis & Short

infirmātĭo, ōnis. f. [1. infirmo], a weakening, invalidating.

  1. I. Rerum judicatarum, Cic. Agr. 2, 3, 8; 2, 4, 10.
  2. II. Transf., a refuting, disproving: judicatio est, quae ex infirmatione et confirmatione rationis nascitur controversia, Cic. Inv. 1, 13, 18; 2, 21, 62.