Lewis & Short

dūresco, rui, 3, v. inch. n., to grow hard, to harden.

  1. I. Prop.: durescit humor, * Cic. N. D. 2, 10, 26; so in the praes.: limus, Verg. E. 8, 80: campus, id. G. 1, 72: corpus, Ov. M. 8, 607: curalium, id. ib. 15, 417: oraque duruerant, id. ib. 2, 831: durescente materia, Tac. G. 45.
  2. II. Trop.: in alicujus lectione, qs. to become ossified, Quint. 2, 5, 21; 10, 5, 16.