Lewis & Short

sŏpōrus, a, um, adj. [sopor] (poet.), of or belonging to sleep, i. e.,

  1. I. Sleep-bringing, causing sleep: Nox, Verg. A. 6, 390; Luc. 2, 236; Stat. Th. 1, 403: soporae pennae (Somni), Sil. 10, 354: amnis, i. e. Lethe, id. 13, 856.
  2. II. Heavy with sleep, drowsy, dozy: dapibus vinoque soporus, Val. Fl. 2, 222.