Definition of Soporiferous

Adjective: soporiferous  ,só-pu'ri-fu-rus

1. Sleep inducing
   - soporific, somniferous, somnific, hypnogogic, hypnagogic
    
2. Inducing mental lethargy
   "a soporiferous speech";
   - narcotic, soporific

See also:
sopor
soporific