sop·o·rif·ic / ˌsäpəˈrifik/ • adj. tending to induce drowsiness or sleep: the motion of the train had a somewhat soporific effect. ∎ sleepy or drowsy: some medicine made her soporific. ∎ tediously boring or monotonous: a libel trial is in large parts intensely soporific. • n. a drug or other agent of this kind. DERIVATIVES: sop·o·rif·i·cal·ly / -ik(ə)lē/ adv.