Adjective: soporiferous ,só-pu'ri-fu-rus
- Sleep inducing
"The soporiferous effects of the medication made driving dangerous";
- soporific, somniferous, somnific
- Inducing mental lethargy
"a soporiferous speech";
- narcotic, soporific
See also: depressant, lame, lameo [informal], meh [informal], uninspiring, uninteresting