Lewis & Short

lentĭtūdo, ĭnis, f. [lentus], slowness, sluggishness, inactivity.

  1. I. Lit.: conjuratorum, Tac. A. 15, 51; Vell. 2, 11, 2.
  2. II. Trop.: dulness, apathy, insensibility, Cic. Tusc. 4, 19, 43: omnino non irasci est non solum gravitatis, sed nonnumquam etiam lentitudinis, id. Q. Fr. 1, 1, 13, § 38.
    Of speech: libros ejusdem lentitudinis ac teporis, dulness, heaviness, Tac. Or. 21, 6.